More than one in four chief executives of NHS Trusts earn annual salaries of at least £100,000 - but many are still leaving the service.

The turnover of senior staff is 20 per cent, believed to be higher than for any other group of health staff.

A report by pay analysts Incomes Data Services said there had been a big increase in the number of NHS Trust chief executives in the UK receiving six-figure earnings last year.

The massive wave of reorganisation in the NHS, including the merging of trusts, had made an impact on pay levels.

Chief executives enjoyed average pay rises of 5.3 per cent last year, although this ranged from 0 per cent to 35 per cent, according to the analysis of 380 trust annual reports, covering around 90 per cent of the UK total.

Basic salaries ranged mainly from £74,000 to £95,750, with highest rates paid to chief executives in general acute or multiple activity hospital units and lowest in ambulance trusts.

Trusts in the London area were the highest payers while those in the West Midlands were the lowest.

The Institute of Healthcare Management, which represents 8,000 NHS managers, said: "Over the last year chief executives' responsibilities have increased considerably with mergers and reorganisations and this has been reflected in their salaries."

Commenting on the report, a Department of Health spokesman said: "NHS Trust chief executive salaries are not decided centrally by the Government.

"But (these pay rises) ought to be seen in the context of other NHS staff - for example some of the most senior nurses will have a maximum increase of between 6.6 per cent and 6.9 per cent."