The backlash against the audit of parliamentary expenses intensified today with a Labour MP insisting he would not pay back any money.
Alan Simpson said he was ready to go to court rather than return £500 that he has been accused of over-claiming in cleaning bills.
His stand came as Lib Dem leader Nick Clegg was heavily jeered in the Commons after calling for Sir Thomas Legg's review to be even tougher.
Westminster's corridors have been buzzing with talk of a rebellion against the audit findings which have left scores of MPs facing handing back thousands of pounds.
However, strong support from Gordon Brown, David Cameron and other party leaders had kept open dissent to a relatively low level.
Mr Simpson told BBC Radio 4's Today programme that Sir Thomas had got it "profoundly wrong" and risked "making an ass of himself".
"If he thinks that the principle of him coming in and retrospectively re-writing the rules would stand up before the courts, then I think he should test it before the courts," the Nottingham South MP said.
"I just want to give him the opportunity to reflect on something he has got profoundly wrong.
"I don't want to push him into going before the courts and making a bit of an ass of himself, but I think it's a corner he might usefully like to take himself out of.
"I can't bring myself to believe that he would be so stupid as to want to stay in that corner."
But writing in the Daily Telegraph, Mr Clegg insisted that Sir Thomas's review had not yet gone far enough.
"I think most people expected the worst offences to come under the toughest scrutiny - MPs who avoided capital gains tax, claimed cash for mortgages that didn't exist or 'flipped' their second home so they could claim for renovations on house after house," he wrote.
Many MPs made their views on Mr Clegg's intervention clear later, greeting him with a barrage of catcalls as he stood up to speak at Prime Minister's Questions.
However, there was no overt mention of the scandal, with Afghanistan dominating the first session back after the summer.
Sir Thomas sparked the controversy by setting new retrospective limits on claims, of £1,000 a year for gardening and £2,000 for cleaning - meaning MPs were now being asked to repay spending that was signed off by Commons officials.
Anne Begg, Labour MP for Aberdeen South, who was cleared by the review, said there was an "understandable feeling" among MPs that the rules had been changed unfairly.
She said that "quite a number" of MPs were "quite upset" that they have been asked for documents they have already provided to the Commons Fees Office.
"That is causing extra stress and upset for them and it's understandable how they feel," she told BBC Radio Scotland.
Harriet Harman, Leader of the House of Commons, said: "I don't think this is going to be sorted out by legal action, and nor really is it going to be sorted out by a competition between the political parties.
"This is an issue for the whole House of Commons to do what is necessary to restore public confidence."Reuse content