Governments whips last week conceded that they face defeat if the recommendations of the Top Salaries Review Body, thought to be arguing for an increase of around pounds 8,000 a year for office expenses, are not offered to MPs.
The recommendation, believed to be linked to a restructuring of the allowance system, will be considered by the Cabinet this week and by the House of Commons the week after.
Stan Orme, outgoing chairman of the Parliamentary Labour Party, who has demanded implementation of the report's recommendations, said MPs needed the funds to pay a full-time secretary and researcher. 'Among the new intake there is a growing impatience that facilities are not adequate for the job and that pressure will continue,' he said.
The allowance system has been a long-running source of complaint from MPs, especially those in opposition who are denied the resources of Whitehall. In 1986 Labour MPs ambushed the Government - which then had a much larger majority - by winning support for a rise in the office cost allowance from pounds 13,211 to pounds 20,140. Many MPs believe the system needs overhaul and one Labour MP last week described it as 'inadequate for those who work hardest - but open to abuse for those who don't'.
Ask MPs how much they need and the most common retort is 'How long is a piece of string?' One Tory MP said last week: 'If we were offered pounds 500,000 for our office expenses I could spend it. It would make me unbeatable in the constituency, with staff crawling all over every possible local issue.'
Another Conservative argued that he needed a living allowance to help keep up a decent-sized constituency home to entertain and occasionally accommodate visiting ministers.
The history of payment to Parliamentarians is a tortuous one. Salaries were introduced only in 1911, and the backbench or opposition MP's pay is now pounds 30,854.
Allowances have burgeoned since the Sixties, when only telephone calls in London, free postage for Government correspondence, free official publications and a travel allowance were provided.
Stationery, inland phone calls and postage services from Parliament are now free to members. An MP can also claim an office cost allowance - to cover both Westminster and constituency offices - of up to pounds 28,986.
Although this money has to be accounted for, most MPs claim up to their limit, spending any balance on new equipment, for example. One MP said last week that, if any cash was left unaccounted for, he filled in an invoice for overtime work and gave his secretary a cash bonus.
Here there is a potential for abuse, if, as in many cases, the MP's secretary also happens to be his wife (or - much more rarely - her husband). While most of these appointments are bona fide with the partner working hard, caseloads vary greatly.
In addition MPs with seats outside inner London can claim up to pounds 10,786 a year for overnight expenses incurred on parliamentary duty away from home. This can be used to pay rent, hotel bills or the interest on a mortgage. Those who own properties and have paid off loans can use up their allowance by claiming incidental costs such as meals.
Travel is also a point of contention. MPs are entitled to unlimited first-class travel warrants for train or air transport between London, the constituency and any other home. Spouses and children under 18 can make make up to 15 return journeys each year.
Moreover, within this 'triangle' of home, constituency and Westminster - and for journeys within the constituency - MPs can claim unlimited (though taxable) mileage at rates of up to 68.2p per mile. Making few concessions to the green lobby, MPs get more cash the bigger their car.
These rates drop for claims over 20,000 miles and if an MP claims more than 25,000 miles a year he or she may be asked for details of all journeys.
Claims vary widely, according to the Fees Office, between those who drive to and from Scotland and those who take a bus from the East End of London. Though stories abound of 'car pools', which allow MPs to claim for shared journeys, most MPs are too busy to co-ordinate trips with their colleagues.
For hard-pressed and energetic MPs with a large workload and party political ambition, the funding is inadequate. Chris Smith, MP for Islington South, who led the Commons rebellion in 1986, said: 'The system does need reform, allowances do need to increase. I want to see a situation where an MP can employ two constituency caseworkers and one researcher appointed by the MP and funded properly by the Fees Office.'
MPs' cash entitlements
Salary 30,854 pounds
Office costs allowance 28,986 pounds
London Supplement and Additional Allowances 10,786 pounds
Total 70,626 pounds
Free stationery, inland telephone calls and postage from Westminster
Free first-class rail or air travel between Westminster, constituency and second home or mileage of up to 68.2p per mile for the first 20,000 miles
Limited free travel for spouses and children under 18
Free parking at Westminster
Resettlement grant for any MPs who lose their seat equal to a minimum of 50 per cent of salary