Four MPs have confessed that they are working less than 35 hours a week for their current salary of pounds 34,085.

During Commons holidays - which accounted for 17 weeks in the last full parliamentary year - more than 50 MPs said they worked less than a 35- hour week.

As MPs prepare to vote themselves a pay rise in the Commons on Wednesday, with a choice between John Major's call for a restrained 3 per cent and the 26 per cent recommended by the Senior Salaries Review Board, some backbenchers might be embarrassed by the revelation that colleagues do so little for their money.

But questionnaires filled in by MPs as part of the review body examination shows that 1 per cent of the 411 backbenchers who replied volunteered that they worked less than 35 hours a week - even when the House was in full session.

The self-confessed shirkers are likely to be among the 28 per cent of MPs who did not spent any time at all attending select or standing committees, which carry out the critical scrutiny of Whitehall work and the line-by- line examination of legislation.

Among the more assiduous, more than 30 MPs said they worked more than 90 hours a week when the Commons was in session.

The review body says: "For constitutional and practical reasons we have discounted the possibility of performance-related pay for MPs, whatever its utility may be elsewhere." Having supported the system for the rest of the public service, Parliament is to be excused.

But the report does add that the review body will "consider further ... whether to make recommendations on the structure of additional remuneration for holders of certain positions of additional responsibility in the House."

That could mean a cash bonus for Opposition frontbenchers, and MPs who chair committees.

As for backbench pay, more than 60 MPs told the review body that they were worth twice as much as the current salary of pounds 34,085 - and about 8 MPs said they were worth more than pounds 90,000 a year.

Conversely, more than 30 full-time secretaries, employed by MPs, said they were paid less than pounds 10,000 a year. Of the 477 staff who replied to questionnaires, only 6 per cent got more than pounds 25,000.

The report said: "There is no doubt that the workload of conscientious MPs is heavy, but heavy workloads can be found in many walks of life and at different levels of salary.

"Pay cannot be set by reference to a recognisable 'market rate'. There is no evidence of a shortage of persons willing to seek selection as candidates ... nor is there any way in which the quality of MPs can be readily assessed."

Time and motion - the inside view

What a survey of 411 MPs discovered

Those who believe their work is worth less than pounds 35,000 4%

Worth more than pounds 50,000 61%

Worth pounds 70,000-pounds 90,000 4%

Worth more than pounds 90,000 2%

Those working less than 35 hours a week in session 1%

Working less than 35 hours a week in recess 13%

Working less than 50 hours a week in session 6%

Working more than 70 hours a week in session 48%

Working more than 90 hours a week in session 8%