Hospitals investigated for having higher-than-expected death rates will be ordered to undertake an urgent review of their staffing levels, reports suggest.

The 14 hospital trusts are expected to be criticised over low numbers of staff - particularly nurses.

NHS England medical director Professor Sir Bruce Keogh will reveal that all of the trusts bar one had a lower ratio of nurses to patients than the national average, the Daily Telegraph reported.

It is expected that the report will suggest there is a link between inadequate staffing levels and poor standards of care.

Sir Bruce will describe poor care, medical errors and management blunders at the trusts. He will suggest that the Stafford hospital scandal, where as many as 1,200 patients may have died unnecessarily due to poor care, was not a one-off.

Reports suggest that there may have been 13,000 needless deaths across the 14 trusts since 2005. Following the publication of the report of the public inquiry into serious care failings at Mid Staffordshire, Sir Bruce launched an investigation into the 14 other trusts because of their high mortality rates.

Nine of the trusts have been ''outliers'' on the Hospital Standardised Mortality Ratio (HSMR) for two years running and the other five were identified by the Summary Hospital-level Mortality Indicator (SHMI), which compares the number of patients who died following admission to hospital with the number who would be expected to die, as having higher-than-expected death rates.

The latest SHMI data, published in April, suggests that as many as 3,000 people may have died needlessly in just one year at the 14 trusts.

But the Guardian reported that Sir Bruce will say it is "meaningless" to use mortality indicators to quantify actual numbers of avoidable deaths. The newpaper said his report will say: "However tempting it may be, it is clinically meaningless and academically reckless to use such statistical measures to quantify actual numbers of avoidable deaths."

The trusts which have been under review are: Basildon and Thurrock University Hospitals NHS Foundation Trust, Blackpool Teaching Hospitals NHS Foundation Trust, Buckinghamshire Healthcare NHS Trust, Burton Hospitals NHS Foundation Trust, Colchester Hospital University NHS Foundation Trust, The Dudley Group NHS Foundation Trust, East Lancashire Hospitals NHS Trust, George Eliot Hospital NHS Trust, Medway NHS Foundation Trust, North Cumbria University Hospitals NHS Trust, Northern Lincolnshire & Goole Hospitals NHS Foundation Trust, Sherwood Forest Hospitals NHS Foundation Trust, Tameside Hospital NHS Foundation Trust and United Lincolnshire Hospitals NHS Trust.