The NHS medical director Sir Bruce Keogh is to investigate trusts with high death rates “and check remedial action is being taken”, the prime minister has told Parliament.

He said this would begin “immediately” ahead of the start of the new inspections regime in the autumn.

The NHS Commisioning Board this afternoon announced the five trusts would be Colchester Hospital University Foundation Trust, Tameside Hospital Foundation Trust, Blackpool Teaching Hospitals Foundation Trust, Basildon and Thurrock University Hospitals Foundation Trust and East Lancashire Hospitals Trust.

The two main mortality indicators currently are the hospital standardised mortality ratio produced by Dr Foster and summary hospital mortality indicator produced by the NHS Information Centre.

Both measures compare an expected mortality rate for the trust based on its case mix and patient volume against the deaths actually recorded at the trust to give a “higher than expected” or “lower than expected” score.

The trusts announced by the commissioning board do not tally exactly with the outlier trusts identified by the NHS Information Centre last year.

Data for the second full year, 2011-12, was published in October 2012. Four trusts had a higher than expected mortality rate in each of the datasets published so far. They are: Blackpool Teaching Hospitals Foundation Trust, George Eliot Hospital Trust, East and North Hertfordshire Trust and Tameside Hospital Trust.

Many of the hospitals concerned dispute the methodology or point out their score is improving and that other factors can explain an above-average mortality rate.

After death rates pointed to Mid Staffordshire Foundation Trust as an outlier the strategic health authority commissioned its own study disputing the Dr Foster findings, something Robert Francis QC criticised it for.

Sir Bruce, a cardiothoracic surgeon who pioneered the release of mortality data for heart surgery, is also leading a review of the definitions and specification of accident and emergency departments for the commissioning board.

Royal College of Surgeons president Professor Norman Williams said his organisation was working to make more data available.

He said: “We are now preparing for the publication of surgeons’ results later this year and welcome the report’s commitment to the publication of proper outcomes data which is publically funded.

“The surgical profession believes this will help reduce mortality rates through greater scrutiny, drive down poor performance and ultimately empower patients.”