Fresh questions have been raised about the expenses claims of beleaguered Culture Secretary Maria Miller, as it was reported that she stopped claiming a second home allowance at around the time MPs were asked to sign a declaration that they would pay tax on any such property when it was sold.
The Daily Telegraph said that redesignating the house she shared with her parents in Wimbledon, south London, as her main home would mean that no capital gains tax was payable when it was sold at a reported profit of £1 million earlier this year. The tax is levied at 28% on profits made on the sale of second homes.
But a spokesman for Mrs Miller denied that she had changed her second home designation in order to avoid having to sign the declaration, pointing out that the first of three letters from parliamentary authorities was not sent until May 2009, and she stopped claiming all accommodation allowances in April that year.
Following the expenses scandal, Mrs Miller did not claim second home expenses on any property, said the spokesman.
The spokesman said: "It is well documented that Maria stopped claiming any accommodation allowance at all in April 2009.
Pressure was mounting on Prime Minister David Cameron to sack Mrs Miller, whose apology to the House of Commons last Thursday has failed to draw a line under the expenses issue.
Former Conservative chairman Lord Tebbit became the most senior Conservative to call for her to go, writing on the Telegraph website that her "arrogant" handling of the scandal had revived voter anger over MPs' expenses and adding: "The best way out of this is for Mrs Miller to resign."
A poll by Survation for the Mail on Sunday found that large majorities of voters believe she should forfeit her Cabinet post (78%) or be sacked as MP for Basingstoke (68%).
Ominously for Mrs Miller, 82% of those identifying themselves as Tory supporters thought she should be removed as Culture Secretary.
Meanwhile, a Conservative member of the Commons Standards Committee which told Mrs Miller to apologise rejected calls for MPs to be stripped of the power to police their own behaviour.
The committee overruled independent standards commissioner Kathryn Hudson, finding that Mrs Miller should repay £5,800 in overclaimed expenses rather than the £45,000 recommended by the
Expenses watchdog Sir Ian Kennedy, chair of the Independent Parliamentary Standards Authority, said it was time for MPs to stop "marking their own homework" and give Ms Hudson the final say in standards investigations.
And Labour's shadow leader of the Commons Angela Eagle promised a shake-up if the party wins next year's election: "We need a system which commands public confidence, and what we have at the moment clearly doesn't do that.
"We need reform so that people have faith that MPs are properly held to account. David Cameron has failed to act but Labour won't let this failing system go unreformed."
But Standards Committee member Geoffrey Cox warned that handing the right to sanction MPs to an external regulator could raise constitutional issues, as the watchdog could have the power to change the shape of a government - particularly in times of a narrow majority - by handing down a lengthy suspension or even expulsion from the Commons.
Mr Cox told BBC Radio 4's Westminster Hour: "Anybody who has the power to expel a Member of Parliament from the House of Commons has an enormous power to alter governments, to change the shape of political history.
"I think what the critics of the current system have to answer is if external regulation is going to be introduced, who is to do it, and to whom is that person or regulator to be accountable?"
While MPs are accountable to the electorate through the ballot box, in the case of an independent regulator "the only conceivable possibility would be to hand it to a court", said Mr Cox.
"That would involve real problems, constitutional problems, of the separation of powers. I'm not at all sure the judiciary would want to have the powers," he said.
And the Torridge & West Devon MP added: "Nowhere in the world - certainly in no major democracy - has there been complete external regulation."
Work and Pensions Secretary Iain Duncan Smith suggested that Mrs Miller was suffering a backlash for being the minister responsible for the same-sex marriage Bill, which was deeply unpopular with many grassroots Tories.
Speaking on BBC1's Andrew Marr Show, Mr Duncan Smith said: "I think she has done a very good job in a very difficult set of circumstances, with the Leveson Inquiry, which has stirred up a lot of media antipathy to her.
"And also the gay marriage stuff - there's a lot of Conservatives out there who perhaps weren't necessarily supportive, who also feel rather bitter about that."
Asked if she should rethink her position, he replied: "No, I don't think so."
And he warned: "My view generally is that I'm supportive of Maria, because if we are not careful we end up with a witch-hunt of somebody."
:: Survation interviewed 1,001 voters on April 4 for the Mail on Sunday.
John Mann, the Labour MP whose complaint sparked the commissioner's investigation into Mrs Miller's claims, has asked Commons Speaker John Bercow to grant an urgent question on reform of the Standards Committee.
Mr Mann said: "The Standards Committee's recent decision to overrule the conclusions made by the Independent Commissioner for Standards, Kathryn Hudson, in the case of Maria Miller has highlighted the problem of MPs regulating their own expenses.
"Public trust in Parliament and in the expenses system has now completely eroded, and we need a new, transparent regulatory system.
"The Standards Committee should have its power to rule on MPs' expenses abolished, and more power should be given to the independent commissioner."
"We have to stop the practice of MPs regulating themselves."
He added: "I hope that the Speaker will grant this request, as faith in politicians is at crisis point and urgent action is required."