Prime minister Tony Blair last week moved to pacify health service unions angry that the independence of the pay review bodies had been undermined by new terms of reference set out in the comprehensive spending review.

In a letter to the British Medical Association and Royal College of Nursing, he said the review bodies had been told that the changes would be discussed 'in detail' before they were implemented.

He said there would be no cash limit on review body recommendations. And he promised that health secretary Frank Dobson would 'be in touch shortly' to start talks with the unions.

Newly elected BMA chair Ian Bogle had accused chancellor Gordon Brown of being 'economical with his phraseology' in referring to the changes as a 'further strengthening' of the bodies' remit.

In future they will have to take account of recruitment and retention, output targets, the requirement to stay within three-year spending limits and the government's inflation target - which 'requires responsible pay settlements'.

The BMA, the RCN and leaders of the professions allied to medicine all wrote to Mr Blair after the spending review announcement, setting out their concerns.

Dr Bogle said he welcomed recognition of recruitment and retention problems but was worried that yearly pay settlements would suffer if they were linked to three-year spending plans.

'Output targets are not just the responsibility of doctors - tying their pay to them is totally unfair,' he added.

RCN general secretary Christine Hancock also asked for guarantees that the nurses' review body would not be forced to keep recommendations within a cash limit.

In his reply, Mr Blair said he could 'confirm that the pay review body will not be required to make recommendations within a predetermined cash envelope', and reaffirmed the independence of the review bodies.