Almost 50,000 people could be dying with malnutrition in English hospitals, the Tories claimed today.
A new Government report published today suggests the number of people thought to have malnutrition in hospital is an underestimate.
Many such patients are already malnourished before they enter hospital although they can deteriorate on the wards.
Campaigners say there is a lack of help with eating in hospitals alongside a failure to recognise the severity of the problem.
Yesterday's inquiry report into Mid Staffordshire NHS Foundation Trust noted some patients were left without food and water for days at a time.
Around half of families questioned said there were issues with obtaining meals and drinks.
The latest end-of-year report from the Nutrition Action Plan Delivery Board said 239 patients died because of malnutrition in English hospitals in 2007.
Overall, 2,656 were reported to have died from malnutrition in hospitals and care homes since 1997, it added.
The report's authors said: "However, we believe that these statistics can be very misleading.
"They represent less than 0.5% of the number who died in hospital with malnutrition.
"We know that malnutrition predisposes to disease, it delays recovery from illness and it increases mortality.
"It follows that the effect of malnutrition on mortality rates is substantially greater than the number reported to have died because of malnutrition."
Extrapolation by the Tories suggests this means 47,800 people died in hospital with malnutrition in 2007.
The report was delivered to the Government in August 2009 but has only been released today.
Shadow health minister Stephen O'Brien said: "It is horrific that so many patients are dying with malnutrition.
"We have raised this issue many times but Labour ministers have dragged their feet and are doing very little about it.
"The Government has sat on this devastating report since last summer - it is tragic to think that many more lives might have been saved if they hadn't deliberately delayed publishing it because of the embarrassment it causes them.
"The Government urgently needs to take this report and its recommendations seriously.
"And it needs to free doctors and nurses from a culture of box-ticking and bureaucracy so that every patient can get the care they need in hospital."
More than seven million people in the UK are vulnerable to malnourishment - around 150,000 people in hospitals, 600,000 people in care homes, 700,000 people in sheltered accommodation and six million who are dependent on others for their food and water needs, today's report said.
Malnutrition affects more than 10% of older people, with 93% of people suffering from malnutrition living in their own homes, according to the British Association for Parenteral and Enteral Nutrition (Bapen), which studies the issue.
Malnutrition is also likely to affect patients recently discharged from hospital and those with conditions like dementia or cancer.
Pensioners aged over 65 make up around 1.3 million of the three million people in the UK at medium or high risk of being malnourished, despite accounting for only 16% of the population, according to Bapen.
Michelle Mitchell, charity director for Age Concern and Help the Aged, said: "Despite thousands of older people dying in hospital while malnourished each year, the failure of health ministers to lay out any concrete actions to tackle the problem will mean this scandal will continue.
"It is hugely disappointing that despite a lot of goodwill and excellent work among some individual hospital trusts, ending malnutrition has been reduced to a talking shop by the Government.
"We launched the Hungry to Be Heard campaign over three years ago to demand action from the Government.
"We know one million older people in the community are malnourished, yet there is still no evidence of any real progress on this problem."