A new deal with Scottish hospital consultants could cost double what was originally expected.

The new contracts came into effect on Thursday for around 3,000 members of staff. They are designed to help them better manage their workloads.

The arrangement involves paying higher rates to consultants who dedicate their overtime hours to NHS work, rather than to patients in the private sector. Two years of negotiations preceded the eventual agreement, signed in September 2002.

There are fears the move could plunge Scottish NHS trusts deeper into debt. BBC Scotland reports that NHS Lothian faces an £8 million bill, £5 million more than expected, while costs have doubled in the case of Glasgow's health board.

The British Medical Association argues that the inaccurate estimates were due to mistakes in accounting, while some claim there has been confusion over the number of hours that consultants actually work.

Health minister Malcolm Chisholm admitted that there would be a two-month delay in implementation of the contracts, as each individual doctor's role has to be assessed.

"We must get the job plans of consultants correct, there is a lot of extra money going to consultants - quite rightly - but in exchange for that consultants must give a proper account of what they do, they must guarantee the hours they spend in hospitals and they must put their NHS work first," he said.

He conceded that the new contracts were "a bit more expensive than originally envisaged".

"The costings [that were previously completed] were not absolutely correct," he added.

"However, I sent out an extra £30 million to health boards just last week to help with this very exciting process of modernisation."