Data released by health information service Dr Foster Intelligence found that Chesterfield Royal Hospital had 1.34 nurses and 2.41 qualified medical staff per bed following an analysis of staffing levels at 147 trusts between April 1, 2007 and March 31, 2008.

The Royal was one of ten trusts with the lowest staffing ratios and a 'high' mortality rate – 106.98, seven per cent higher than the expected level of 100.

The research comes after the Healthcare Commission identified chronic staff shortages as a key reason for failings at Mid Staffordshire NHS Foundation Trust where up to 400 people more than would have been expected died over a three year period.

The under-fire trust, where Royal chief executive Eric Morton has been brought in temporarily as a trouble-shooter, had higher staffing ratios than Chesterfield – 1.39 nurses and 2.54 qualified staff per bed.

Dr Peter Carter, chief executive and general secretary of the Royal College of Nursing, said: "It's very simple — when hospitals do not have enough nurses, patients are put at risk.

"Hospital trusts must make sure that by having enough nurses they keep all their patients safe."

But Royal chiefs said the Dr Foster figures under-represented current staffing at the hospital – which has 592 beds – not taking into account about 80 senior nursing positions across the trust and 26 additional nursing posts recently appointed following a review last year.

A spokesman added: "We are confident that nurse staffing levels are robust – and the board of directors, under the Chief Nurse's lead, regularly reviews the position to ensure this is maintained and action taken if necessary."

She said the report's data on hospital mortality rates used different criteria based on an old model and the trust now fell within the 'average' rating.
The Dr Foster Intelligence research identified South Tyneside NHS Foundation Trust as having the lowest nurse and qualified staff to bed ratio – 1.08 and 1.92 respectively with an 'average' mortality rate.

Guy's and St Thomas' had the highest at 2.81 and 5.24, coupled with a 'low' mortality rate.

Dr Simon Jones, chief statistician at Dr Foster Intelligence, said the data showed nursing levels were an important factor in ensuring a low hospital death rate, but other factors, such as the number of local GPs, should also be recognised.