Twenty-five NHS trusts in England should be investigated over higher than normal death rates, a leading health expert has warned the government.

Prof Brian Jarman said a total of 4,600 more patients had died at those trusts in 2007-08 than would be expected.

He told the BBC a higher than expected death rate did not necessarily prove hospitals were doing anything wrong, but could help identify wider problems.

The government said trusts with high death rates had already been checked.

Mortality alerts

Prof Jarman, who is an emeritus professor at London's Imperial College School of Medicine, told the BBC he had identified a number of NHS trusts in England with a higher than expected Hospital Standardised Mortality Ratio (HSMR).

He argues that, when combined with other factors, a high HSMR can indicate broader problems with patient care.

THE 25 TRUSTS

• Barking, Havering and Redbridge University Hospitals NHS Trust
• Basildon and Thurrock University Hospitals NHS Foundation Trust
• Blackpool, Fylde and Wyre Hospitals NHS Foundation Trust
• Central Manchester University Hospitals NHS Foundation Trust
• Colchester Hospital University NHS Foundation Trust
• George Eliot Hospital NHS Trust
• Great Western Hospitals NHS Foundation Trust
• Heart Of England NHS Foundation Trust
• Hull and East Yorkshire Hospitals NHS Trust
• James Paget University Hospitals NHS Foundation Trust
• Mayday Healthcare NHS Trust
• Mid Cheshire Hospitals NHS Foundation Trust
• Mid Staffordshire NHS Foundation Trust
• Mid Yorkshire Hospitals NHS Trust
• North Middlesex University Hospital NHS Trust
• Pennine Acute Hospitals NHS Trust
• Royal Bolton Hospital NHS Foundation Trust
• Sherwood Forest Hospitals NHS Foundation Trust
• Southampton University Hospitals NHS Trust
• Stockport NHS Foundation Trust
• Tameside Hospital NHS Foundation Trust
• United Lincolnshire Hospitals NHS Trust
• University Hospital Birmingham NHS Foundation Trust
• University Hospitals Coventry and Warwickshire NHS Trust
• Wrightington, Wigan and Leigh NHS Foundation Trust

"There are 25 hospitals which have an HSMR which is extremely high, and [where] we have found four or more mortality alerts," he said.

A mortality alert is triggered by higher than expected deaths for a particular procedure.

Prof Jarman said each of the trusts in question had at least 150 more deaths than expected in the year 2007-08.

Across the 25 trusts, there were 4,600 unexpected deaths in total.

He acknowledged there may have been some problems with the way the deaths were recorded, but called on the government to ask the Care Quality Commission (CQC) to investigate each of the trusts rather than relying on their own self-assessments.

"These are ones which I would think it would be worth investigating.

"I have sent the data to the Secretary of State Andy Burnham. I haven't had a response."

The self-assessment system has been widely discredited, and Prof Jarman, a former British Medical Association president, is a long-standing critic of it.

Earlier this month, the BBC's Panorama programme highlighted the discrepancy between many hospitals' own assessments of their performances and the conclusions of inspectors who carried out investigations.

Prof Jarman said: "The regulator uses a method which I think is fundamentally flawed, which is that only 20% of hospitals are inspected every year.

"They are assessing 20% of the cases in the hospital. So that's 20% of 20% which is 4%.

"But when you look at that 4% and see whether the self-assessment agrees with the actual on-site inspection for the hospitals that are at risk, two-thirds of the self-reporting is in fact incorrect."

In response, health minister Mike O'Brien said: "We'll look at Professor Jarman's letter, but the CQC has conducted a regional review of all the trusts identified as having high mortality ratios.

"It confirmed in January that - at that time - they had no current concerns that they would be as bad as Mid Staffordshire clearly was."

Last month an independent inquiry into the Mid Staffordshire NHS Trust detailed evidence of systematic failings which caused "unimaginable" patient distress and suffering, despite being rated as a "fair" hospital by the NHS for most of the period in question.

Last year it had been reported there were at least 400 more deaths than expected at the trust from 2005 to 2008.

Unannounced visits

Mr O'Brien acknowledged that the self-assessment system does have limitations.

"Self-assessment I think has in the past been over-relied upon and that's why we've changed the way in which regulation is carried out.

"In the new system of registration, every hospital gets visited every two years, but if there's a higher risk then it'll be more often than that - and [the CQC] can make unannounced visits at any time," he said.

"What they do not do is leave unchallenged the views of hospitals about the way in which they are behaving."

And the minister warned that, under the new rules, a hospital which failed to meet adequate standards could face having its registration made conditional or even removed altogether, meaning it would no longer be able to operate.

The Report is on BBC Radio 4 on Thursday, 25 March at 2000 GMT. You can also listen via the BBC iPlayeror download the podcast.