What is a main home? For years MPs have been answering by applying common sense, financial self-interest and — most importantly — a little bit of guidance from the Parliamentary Fees Office.

The way that MPs have been answering this question over the past six years has become today a matter of political survival.

The question goes to the heart of the current furore over expenses, since MPs can claim the £24,000 allowance only on the property they designate as their second home.

While substantial sums of taxpayer money have been spent on fixtures and fittings of the family-funded second home, it turns out that MPs have been using rooms in private members’ clubs and other MPs’ flats as their “main home”.

MPs are now facing the full fury of the public. Most tarnished MPs are replying that the arrangement was within the rules — implicitly blaming the Fees Office, now the Department of Resources, for agreeing in the first place. So how did the Fees Office allow such apparently unsatisfactory situations to develop?

Last year the man in charge of checking MPs’ expenses declared that he had virtually no ability to scrutinise their claims beyond a “common sense” test. Andrew Walker, the Commons resources director, said that responsibility for policing expenses lay with voters; they could eject an MP from Parliament if he or she had been exploiting the system.

His remarks indicated the ease with which MPs were able to claim anything they wanted. Yet today, after 15 further months of furore, he remains in his post, apparently unharmed by the devastation that decisions by his department have wreaked on the political process.

Mr Walker said it was not his job to blame MPs who appeared to claim too much. “Members are elected by voters in their constituencies to represent them. Constitutionally they are accountable ultimately to the electorate. This is reflected in \,” he said.

“There is an ultimate responsibility for the member because of the constitutional position. There are limits . . . to which I or my staff can look beyond the claims and the information we receive. Therefore, for the most part we don’t walk into constituency offices. What we do check is that the original claim is sensible.”

He acknowledged that for the first few years after he started the job in 1997, the additional costs allowance might have been used by MPs in effect to write a cheque to themselves, although he emphasised that the system had improved. In other words, before 2002 the system was a free-for-all, with MPs not having to submit mortgage papers to support claims for mortgage interest.

But even today the system of claims is too lax. It turns out that MPs don’t even explicitly declare the location of their “main home”. The forms require only the address of their “second home” for allowance purposes to be listed, making it easier to nominate a private members’ club as a “main home”.

Many will question whether Mr Walker’s sympathies are with MPs or the public. Opposing the release of MPs’ receipts to the public under freedom of information last February, Mr Walker said: “There might very well be a degree of curiosity . . . that went beyond the necessary public interest.”

Today that “curiosity” has turned into a full-blown political crisis.

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