Around 3,000 more patients have died than expected at one of the country's largest NHS trusts in the past 11 years, according to experts at Imperial College London.
Bosses at Pennine Acute Hospitals NHS Trust (Pahnt) and health regulators are accused of ignoring vital data that might reveal substandard and avoidable clinical practices.
Professor Sir Brian Jarman, whose team carried out the analysis, warned that it was dangerous to ignore or dismiss the data, as high death rates signify wider problems in three-quarters of cases.
In 2007, the Imperial team's work sparked warnings about patient care at Mid Staffordshire NHS Trust, which eventually led to a health-watchdog investigation that exposed widespread substandard care of patients. Reports of high death rates at Mid Staffs were rejected or ignored for a decade beforehand.
Three times as many patients have died unexpectedly at Pahnt since 1996 than at Mid Staffs. However, the trust, formed after four hospitals in Bury, Rochdale and Oldham merged in 2002, is significantly bigger.
Professor Jarman, a former president of the British Medical Association, expressed frustration yesterday at attempts by some trusts, regulators and doctors to discredit his team's data. "We have never said the HSMR [Hospital Standardised Mortality Ratio] data is everything," he said, "but it should alert people. In three-quarters of cases, the high death rates cannot be explained away by chance; it should not just be ignored. If I was on the Pennine trust board, I would be worried. Too few people are willing to speak out in the NHS because there is a climate of fear, so I will."
Cure the NHS, the pressure group which successfully fought for an independent inquiry at Mid Staffs, will launch a campaign to expose failings and improve patient care at Pennine this week. The move coincides with an inquest into the death of Lucy Joan Watkin, 77, who died in hospital in 2005 weighing less than six stone. Her family believe inadequate care over months at Pahnt's Fairfield General Hospital contributed to her death.
In a second inquest last month, a coroner ruled that systematic failures at another trust hospital, the Royal Oldham, led to the death of Arnold Siddal, 47, who was left untreated for 14 hours after suffering head injuries during an assault in a pub in 2007.
Patient-safety campaigners say that Pennine highlights a slack attitude among some trusts and the health regulator, the Care Quality Commission (CQC), resulting in patients suffering harm – or dying – before simple safety measures are taken.
Peter Walsh, the chief executive of Action against Medical Accidents, said: "Mortality rates have to be one of, if not the most important indicators of potential problems with patient safety. It appears the CQC are waiting for a 'perfect storm' of a raft of indicators before they will recognise a potential Stafford and take action. We have to have a more robust and proactive system."
Former independent MP and health select committee member Dr Richard Taylor said: "This data is crucial. The Trust should have an explanation for the high figures and, if not, alarm bells should sound. I hear about abysmal care in some hospitals so we cannot say there are no more Mid Staffs out there."
Yesterday, the CQC insisted "there was no evidence of systemic failures at Pennine". Richard Hamblin, CQC director of intelligence, said that judging any trust on its HMSR alone would be "inaccurate and irresponsible". The CQC also looked at information from patients, regulators, scanned infection rates, readmission rates and hundreds of other pieces of intelligence. "All of this together gives the true picture of quality of care," he said.
But critics say the CQC is not properly investigating complaints. Last month it inspected the United Lincolnshire Hospitals Trust, which also has high mortality rates. The inspection came several weeks after it received detailed information, from Gary Walker, former chief executive of the trust, about patients being harmed.
While its final report is yet to be published, no significant safety concerns were identified by inspectors. But several senior doctors and managers with documentary evidence of patient-safety breaches say they were not interviewed. An employment tribunal later this year will hear Mr Walker's claims that he was sacked for refusing to put targets ahead of patient safety.
A Department of Health spokesperson said: "Any trust with a high HSMR should examine whether quality of care is a concern. Action should not stop until they are satisfied that any issues have been effectively dealt with."
Dr Ruth Jameson, medical director at Pahnt, defended its record on patient safety. "Comparing mortality hospital by hospital is fraught with difficulties ... We monitor mortality closely and this is reported to the board monthly and published on our website. It shows our mortality rate has fallen year-on-year ... we have saved 832 additional lives in two years."
'Written off': The grandmother left to fend for herself
Lucy Joan Watkin, 77, died in hospital in September 2005 weighing 37kg – less than six stone. She spent much of the last year of her life in and out of Fairfield Hospital. The vivacious grandmother was admitted to hospital from her home in Bury, Lancashire, to investigate a poor appetite, but almost immediately she was declared 'not for resuscitation' without any consultation with her or her children.
Dangerously low haemoglobin levels caused by myelodysplasia, a chronic blood condition, were detected but several days passed before she was given a blood transfusion. She had no appetite and needed much cajoling to eat and drink, but her relatives were banned from meal times, so she was left to fend for herself. During brief spells at home, she would regain her strength, but without her family to help, the protein and calorie supplements prescribed by the dietician were rarely added to Mrs Watkin's drinks. Her eldest daughter, Janet Watkin, would visit her every day and find full cups of cold tea, uneaten meals and untouched medication sitting on her bedside table. "Mum lost 6kg during one 70-day admission, she was so frail, but they discharged her home as 'fully independent'.
It took me 20 minutes to help her upstairs into her flat. Some of the nurses said she was 'difficult' but she wasn't, not at all. Others said she had dementia; her memory was poor so she didn't remember to eat. But she also had an enlarged spleen, detected by an ultrasound and CT scan in December 2004; it's in her medical notes. This somehow got forgotten or was overlooked, yet it may have been the root cause of her poor appetite. My mum was dehydrated and very, very weak when she eventually died in an armchair at Ramsbottom Cottage Hospital. She was never taken seriously, another elderly person written off from the start."