Mike Adamson, the charity's chief executive, said the phrase was justified by the scale of the “threat” posed to the nation's health and wellbeing by pressures on the system.
There has been a “significant change” in demand for the Red Cross's help in recent months and the charity is now working in 20 A&Es, he said in an article for The Times.
His renewed warning comes as the head of an influential think tank said the NHS was “buckling under the strain of trying to meet rising demand and still maintain standards”.
Mr Adamson said underfunding of social care and a “plethora” of systemic failures were contributing to a crisis that the charity has a duty to expose.
He said: “We see people discharged from hospital to chaotic situations at home, falling and not being found for hours, not being washed because there is no carer to help them.
”These are people in crisis and in recent weeks we have started talking about this as a humanitarian crisis. We don't say this lightly and we have a duty to say it.
“We are part of a worldwide humanitarian network and our fundamental principle of humanity states we must help to 'prevent and alleviate human suffering wherever it may be found'.
”This humanitarian crisis needs urgent action.
“In considering making this statement, I went back and looked closely at the definition of a humanitarian crisis: It refers to the scale and depth of need facing a population.
”In this case we are seeing large numbers of vulnerable people facing a threat to their health, safety or wellbeing.“
Mr Adamson referred to recent deaths at Worcestershire Royal Hospital as extreme examples, but warned patients were suffering ”prolonged physical and mental distress“ on a broad scale.
The Red Cross came under fire for describing the situation facing the NHS as a ”humanitarian crisis“ as it was revealed on Friday that A&E departments shut their doors to patients more than 140 times in December.
Meanwhile figures showed a third of health trusts in England had issued alerts that they needed urgent action to cope.
Critics said the crisis affecting the NHS was not akin to that faced by refugees of conflict in Syria and Yemen, or famine and drought in the Lake Chad region of central Africa.
On Sunday Theresa May said she did not accept the Red Cross's description, but admitted there are ”huge pressures“ facing the NHS.
Mr Adamson said: ”Of course each of those crises is different. But to the British Red Cross, every crisis is personal.
“From famine to floods to loneliness, it's not just the scale of the crisis that matters. It's that the person affected feels they are in crisis.
”That person suffering on the trolley in a corridor feels at crisis point. The people our volunteers help feel scared and desperate. They feel they are in crisis.
“We are talking about this now because there has been a significant change in the system over recent months.”
Mr Adamson said more funding was needed to boost social care to alleviate some of the pressures facing hospitals, including ensuring the elderly can be safely returned home after treatment.
However, he said there are also “too many boundaries” that hit the ability of doctors and nurses to work efficiently and a “plethora of tiny things”, such as access to wheelchairs, that need addressing.
Health news in pictures
Health news in pictures
1/22 Ketamine helps patients with severe depression ‘when nothing else works’ doctors say
Ketamine helps patients with severe depression ‘when nothing else works’ doctors say
2/22 Playing Tetris in hospital after a traumatic incident could prevent PTSD
Scientists conducted the research on 71 car crash victims as they were waiting for treatment at one hospital’s accident and emergency department. They asked half of the patients to briefly recall the incident and then play the classic computer game, the others were given a written activity to complete. The researchers, from Karolinska Institute in Sweden and the University of Oxford, found that the patients who had played Tetris reported fewer intrusive memories, commonly known as flashbacks, in the week that followed
3/22 Measles outbreak spreads across Europe as parents shun vaccinations, WHO warns
Major measles outbreaks are spreading across Europe despite the availability of a safe, effective vaccine, the World Health Organisation has warned. Anti-vaccine movements are believed to have contributed to low rates of immunisation against the highly contagious disease in countries such as Italy and Romania, which have both seen a recent spike in infections. Zsuzsanna Jakab, the WHO’s regional director for Europe, said it was “of particular concern that measles cases are climbing in Europe” when they had been dropping for years
4/22 Vaping backed as healthier nicotine alternative to cigarettes after latest study
Vaping has been given an emphatic thumbs up by health experts after the first long-term study of its effects in ex-smokers. After six months, people who switched from real to e-cigarettes had far fewer toxins and cancer-causing substances in their bodies than continual smokers, scientists found
5/22 Common method of cooking rice can leave traces of arsenic in food, scientists warn
Millions of people are putting themselves at risk by cooking their rice incorrectly, scientists have warned. Recent experiments show a common method of cooking rice — simply boiling it in a pan until the water has steamed out — can expose those who eat it to traces of the poison arsenic, which contaminates rice while it is growing as a result of industrial toxins and pesticides
6/22 Contraceptive gel that creates ‘reversible vasectomy’ shown to be effective in monkeys
An injectable contraceptive gel that acts as a ‘reversible vasectomy’ is a step closer to being offered to men following successful trials on monkeys. Vasalgel is injected into the vas deferens, the small duct between the testicles and the urethra. It has so far been found to prevent 100 per cent of conceptions
7/22 Shift work and heavy lifting may reduce women’s fertility, study finds
Women who work at night or do irregular shifts may experience a decline in fertility, a new study has found. Shift and night workers had fewer eggs capable of developing into healthy embryos than those who work regular daytime hours, according to researchers at Harvard University
8/22 Breakfast cereals targeted at children contain 'steadily high' sugar levels since 1992 despite producer claims
A major pressure group has issued a fresh warning about perilously high amounts of sugar in breakfast cereals, specifically those designed for children, and has said that levels have barely been cut at all in the last two and a half decades
9/22 Fight against pancreatic cancer takes ‘monumental leap forward’
Scientists have made a “monumental leap forward” in the treatment of pancreatic cancer after discovering using two drugs together dramatically improved patients’ chances of living more than five years after diagnosis.
10/22 Japanese government tells people to stop overworking
The Japanese government has announced measures to limit the amount of overtime employees can do – in an attempt to stop people literally working themselves to death. A fifth of Japan’s workforce are at risk of death by overwork, known as karoshi, as they work more than 80 hours of overtime each month, according to a government survey.
11/22 Over-cooked potatoes and burnt toast ‘could cause cancer’
The Food Standards Agency (FSA) has issued a public warning over the risks of acrylamide - a chemical compound that forms in some foods when they are cooked at high temperatures (above 120C).
12/22 Cervical cancer screening attendance hits 19 year low
Cervical screening tests are a vital method of preventing cancer through the detection and treatment of abnormalities in the cervix, but new research shows that the number of women using this service has dropped to a 19 year low.
13/22 High blood pressure may protect over 80s from dementia
The ConversationIt is well known that high blood pressure is a risk factor for dementia, so the results of a new study from the University of California, Irvine, are quite surprising. The researchers found that people who developed high blood pressure between the ages of 80-89 are less likely to develop Alzheimer’s disease (the most common form of dementia) over the next three years than people of the same age with normal blood pressure.
14/22 Most child antidepressants are ineffective and can lead to suicidal thoughts
The majority of antidepressants are ineffective and may be unsafe, for children and teenager with major depression, experts have warned. In what is the most comprehensive comparison of 14 commonly prescribed antidepressant drugs to date, researchers found that only one brand was more effective at relieving symptoms of depression than a placebo. Another popular drug, venlafaxine, was shown increase the risk users engaging in suicidal thoughts and attempts at suicide
15/22 'Universal cancer vaccine’ breakthrough claimed by experts
Scientists have taken a “very positive step” towards creating a universal vaccine against cancer that makes the body’s immune system attack tumours as if they were a virus, experts have said. Writing in Nature, an international team of researchers described how they had taken pieces of cancer’s genetic RNA code, put them into tiny nanoparticles of fat and then injected the mixture into the bloodstreams of three patients in the advanced stages of the disease. The patients' immune systems responded by producing "killer" T-cells designed to attack cancer. The vaccine was also found to be effective in fighting “aggressively growing” tumours in mice, according to researchers, who were led by Professor Ugur Sahin from Johannes Gutenberg University in Germany
16/22 Green tea could be used to treat brain issues caused by Down’s Syndrome
A compound found in green tea could improve the cognitive abilities of those with Down’s syndrome, a team of scientists has discovered. Researchers found epigallocatechin gallate – which is especially present in green tea but can also be found in white and black teas – combined with cognitive stimulation, improved visual memory and led to more adaptive behaviour. Dr Rafael de la Torre, who led the year-long clinical trial along with Dr Mara Dierrssen, said: “The results suggest that individuals who received treatment with the green tea compound, together with the cognitive stimulation protocol, had better scores in their cognitive capacities”
17/22 Taking antidepressants in pregnancy ‘could double the risk of autism in toddlers’
Taking antidepressants during pregnancy could almost double the risk of a child being diagnosed with autism in the first years of life, a major study of nearly 150,000 pregnancies has suggested. Researchers have found a link between women in the later stages of pregnancy who were prescribed one of the most common types of antidepressant drugs, and autism diagnosed in children under seven years of age
18/22 Warning over Calpol
Parents have been warned that giving children paracetamol-based medicines such as Calpol and Disprol too often could lead to serious health issues later in life. Leading paediatrician and professor of general paediatrics at University College London, Alastair Sutcliffe, said parents were overusing paracetamol to treat mild fevers. As a result, the risk of developing asthma, as well as kidney, heart and liver damage is heightened
19/22 Connections between brain cells destroyed in early stages of Alzheimer’s disease
Scientists have pinpointed how connections in the brain are destroyed in the early stages of Alzheimer’s disease, in a study which it is hoped will help in the development of treatments for the debilitating condition. At the early stages of the development of Alzheimer’s disease the synapses – which connect the neurons in the brain – are destroyed, according to researchers at the University of New South Wales, Australia. The synapses are vital for brain function, particularly learning and forming memories
20/22 A prosthetic hand that lets people actually feel through
The technology lets paralysed people feel actual sensations when touching objects — including light taps on the mechanical finger — and could be a huge breakthrough for prosthetics, according to its makers. The tool was used to let a 28-year-old man who has been paralysed for more than a decade. While prosthetics have previously been able to be controlled directly from the brain, it is the first time that signals have been successfully sent the other way
21/22 Aspirin could help boost therapies that fight cancer
The latest therapies that fight cancer could work better when combined with aspirin, research has suggested. Scientists from the Francis Crick Institute in London say the anti-inflammatory pain killer suppresses a cancer molecule that allows tumours to evade the body’s immune defences. Laboratory tests have shown that skin, breast and bowel cancer cells often generate large amounts of this molecule, called prostaglandin E2 (PGE2). But Aspirin is one of a family of drugs that sends messages to the brain to block production of PGE2 and this means cancer cells can be attacked by the body’s natural defences
22/22 Potatoes reduce risk of stomach cancer
Scientists have found people who eat large amounts of white vegetables were a third less likely to contract stomach cancer. The study, undertaken by Chinese scientists at Zhejiang University, found eating cauliflower, potatoes and onions reduces the chance of contracting stomach cancer but that beer, spirits, salt and preserved foods increased a person’s risk of the cancer
“The British Red Cross has long had a role in supporting the NHS, helping people get home from hospital, providing ambulances, wheelchairs and first-aid training,” Mr Adamson said.
“We will continue to do this as long as they need us. But there must be proper funding that recognises how we as a nation are living for longer with multiple needs.
”We need a new joint approach to solving the problems. Without that, this humanitarian crisis will persist.“
Chris Ham, chief executive of think tank the King's Fund, said in a letter to The Times that a new settlement for health and social care was urgently needed.
He wrote: ”With social care, the number of older people receiving publicly funded care has fallen by more than 400,000 since 2009/10, while the health system is buckling under the strain of trying to meet rising demand and still maintain standards.“