Plans to crack down on MPs’ expenses were in confusion last night after it emerged that a new requirement for receipts for everything costing more than £25 did not apply to food.

A committee on expenses chaired by the Speaker announced yesterday that the amount of petty cash MPs can draw for office expenses would also be reduced from £250 to £50 per month, and that they should record spending in a petty cash book.

From next month they must submit a receipt for any item over £25, a tenth of the current limit of £250. The report decided to consider further the £400 monthly allowance for food for which receipts are not required. Information about this allowance is not available in any public document until today, and emerged at a freedom of information tribunal last month. The report said: “The question of food while working away from home will be considered in the context of the root-and-branch review of allowances and is not covered by this report.”

The committee said that it had considered forcing MPs to submit receipts for all expenses, but decided that would be impractical. It added that some MPs already routinely produced receipts for spending below the £250 limit, indicating that a lower threshold, which will be introduced on April 1, would be “administratively feasible”.

The report noted that “some modest increase” in Commons staff may be needed to cope with the changed rules. The committee is undertaking a review of allowances that began after the Conservative MP Derek Conway was found to be paying his son for “all but invisible” work as a researcher while he was an undergraduate in Newcastle upon Tyne.

Last month Michael Martin, the Speaker, was criticised over taxi fares claimed by his wife and was urged to speed up his committee’s review into the expenses system. Yesterday the office of the Parliamentary Commissioner for Standards confirmed that the complaint was still being considered, but declined to comment further.

The committee said that it would publish proposals for more rigorous checks by the end of this month. The report said: “The new low threshold for claims needs to be underpinned by a more robust regime for audit.”

The committee said that some MPs had suggested a system of random spot checks. “Meetings will be held with the National Audit Office, private firms of accountants, HM Revenue & Customs and the Audit Commission to establish what is the most practical and effective arrangement.”

Martyn Jones, the Labour MP for Clwyd South, became the first member publicly to oppose the changes. He said: “The aim of this review was to safeguard taxpayers’ money. Unfortunately it seems likely that it will waste more than it saves. Monitoring an influx of allowance claim forms will require the Department of Finance and Administration to employ more staff for more hours.”

A spokesman for Gordon Brown said: “The Prime Minister welcomes any steps towards greater transparency in MPs’ expenses.” Challenged on why Mr Brown did not publish his own expenses in full, he replied: “That is not his decision. It is a matter for the House authorities.”

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