Death rates at five NHS trusts have been “higher than expected” two years in a row, figures show.
The mortality ratios at the five English trusts have been "persistently high" between July 2010 and June 2012, according to the Health and Social Care Information Centre (HSCIC).
The Summary Hospital-level Mortality Indicator (SHMI) compares the number of patients who die following hospitalisation at a trust with the number who would be expected to die.
Analysts said that the SHMI was higher than expected at Colchester Hospital University NHS Foundation Trust, Tameside Hospital NHS Foundation Trust, Blackpool Teaching Hospitals NHS Foundation Trust, Basildon and Thurrock University Hospitals NHS Foundation Trust and East Lancashire Hospitals NHS Trust for two years running.
Experts said that the indictor should be seen as an "early warning mechanism" so trusts can examine why their score was higher than expected.
The SHMI data, which includes all deaths in hospital as well as deaths occurring 30 days after discharge, also shows that there were 11 trusts which had higher than expected mortalitybetween July 2011 and June 2012.
While the majority of trusts (115) fell into the "as expected" category, 16 trusts had lower than expected mortality rates in the same time frame.
HSCIC chief executive Tim Straughan said: "Today's report, based on two years of data, shows an emerging picture of which trusts are categorised over time as having higher or lowermortality ratios than expected; and indeed also shows that the vast majority of trusts in England have a mortality ratio that is as expected, based on the characteristics of the patients they will typically treat.
"As always with such a complex area, this mortality indicator should be seen as an early warning mechanism, rather than a definitive judgment, to examine the reasons why a trust's ratio is higher or lower than expected."
Dr Sean MacDonnell, medical director at Colchester Hospital University NHS Foundation Trust, said the trust planned to monitor, analyse and investigate mortality trends.
He said the trust took the mortality indicator "extremely seriously" adding: "The number of deaths at Colchester General Hospital and Essex County Hospital is falling year-on-year.
"In 2011/12, there were 18.28 deaths per 1,000 spells or admissions compared with 20.22 in 2010/11 and 21.42 in 2009/10."
Health Secretary Jeremy Hunt said: "I expect trusts to examine this data carefully and take action to investigate if necessary and ensure they are providing safe, high quality care.
"This data alone cannot be used to judge the quality of care. However, the CQC examines mortality data and a range of other information to target their inspections and to ensure trusts take appropriate action where there are problems.
"Where trusts have a higher than expected ratio, the department will work with strategic health authorities to investigate the underlying reasons for this and ensure that firm action is taken."
A spokeswoman for Blackpool Teaching Hospitals NHS Foundation Trust said that last year the trust took steps to investigate its historically high mortality rates.
Dr Mark O'Donnell, the trust's medical director, said: "We are committed to improving the outcomes for patients and the safety of our services and have already undertaken much work which has now resulted in figures at or near the national average."
Tariq Mahmood, medical director at Tameside Hospital NHS Foundation Trust, said that another mortality indicator - the Hospital Standardised Mortality Ratio (HSMR) - showed that the trust had a "normal" death rate.
"We would like to reassure our patients, relatives and carers that we continue to work with our local health partners to look at all the factors throughout our community which influence this data," he said.
"We take this very seriously as patient safety is our top priority.
"It is important to stress that our mortality rate, as indicated by the HSMR for exactly the same period, was normal. In fact Tameside has had a normal HSMR mortality rate with this indicator for over three years."
Rineke Schram, medical director at East Lancashire Hospitals NHS Trust, added: "The SHMI indicators are very complex and should not be looked at in isolation.
"The population of East Lancashire has some of the poorest health and deprivation indices in the country and it is these indices that are not taken into account when the mortality ratio is calculated.
"The trust agrees that the indicator should be used as a warning signal rather than a judgement and used to examine the reasons why the ratio is high, particularly as other mortality ratios do not give the same result.
"Clinicians at the trust systematically review mortality data from all causes. This includes reviewing every patient's death to see if anything could have been done differently, and looking at trends and patterns in disease categories to see if different treatments or methods of management should be introduced."
A spokeswoman for Basildon and Thurrock University Hospitals NHS Foundation Trust said: "The trust is working hard to improve its mortality ratio performance.
"While the figures relating to July 2010-June 2012 show the trust's mortality rates as being higher than expected, the figures are still within expected limits for our demographic."
She added that the trust reviews all hospital deaths "to see if there are any deficiencies in care".