Labour MP John Mann and Conservative MP Shailesh Vara discuss plans to reform expenses
The man heading an inquiry into MPs' expenses says he is "not surprised" party leaders failed to agree reforms and warned against "quick fix" changes.
Sir Christopher Kelly said a thorough, independent review was needed and urged party leaders to accept his committee's recommendations - due later this year.
Gordon Brown wants to replace the second-home allowance for MPs with a flat-rate fee based on attendance.
But opposition parties reject the move, saying the plans are not transparent.
And, although ruling no options out, Sir Christopher said he did not believe Mr Brown's plan would command public support.
Mr Brown wants a new system of expenses, scrapping the controversial second-home allowance, agreed before the summer.
Despite failing to win the support of the Conservative leader David Cameron and the Lib Dem leader Nick Clegg, the prime minister intends to press ahead with a vote on the issue next Thursday.
'Tide of fury'
Sir Christopher, whose independent Committee on Standards in Public Life begins its review on Thursday, said an independent inquiry was needed to settle the issue once and for all and that a political deal was not "the right way" to go about it.
Ross Hawkins, BBC News political correspondent
"So the Standards watchdog is standing up for himself. That matters because next week the House of Commons will vote on changes to the expenses regime.
Downing Street has tried to create a consensus, but while there is some common ground the Conservative and Liberal Democrat leaders reject the prime minister's daily rate idea.
On the face of it the vote means MPs will come to binding conclusions many months before Sir Christopher finishes his report, and his argument for apolitical advisers to settle the matter has already been lost.
But opponents will use the watchdog's words against the prime minister. Criticism of the flat-rate scheme from Sir Christopher - the non politician in this argument - may prove influential in the House of Commons vote."
His committee would take a "cold, hard look" at MPs expenses, public concern over which was the biggest threat to trust in politics since the cash-for-questions scandal of the 1990s.
While the government is not obliged to accept his committee's findings, he said he believed it was in the interest of all political parties to agree to endorse his recommendations - due to be published before the end of the year.
"I am not interested in a menu of options from which politicians can pick and choose," he said, stressing that he would come up with "a comprehensive set of recommendations".
"Pressure on politicians to accept sensible recommendations will be enormous," he added.
Sir Christopher said recent scandals involving MPs expenses were "not healthy" for democracy and undermined the majority of MPs who "perform their duties with diligence and integrity".
While accepting that Mr Brown wanted to move quickly on the issue, Sir Christopher said he was wary of "piecemeal reforms" which stored up problems in the future.
He said it was "very unlikely" MPs would be able to resolve the issue in a planned vote next week, adding that his task was to "remove it [the issue] from the headlines to enable MPs to get on with doing their job".
Earlier, Sir Christopher suggested an allowance payment based on MPs' daily attendance at Westminster - the central plank of Mr Brown's plan - was unlikely to be accepted by the public.
"I think the public would have great difficulty in the notion that claims for the reimbursement of expenses should not need to be backed by receipts," he told the BBC's Today programme.
Sir Christopher said Mr Brown had assured him the proposed changes were only interim measures ahead of his investigation.
The inquiry has been brought forward its inquiry after newspaper revelations about the use of second-home expenses by ministers.
Home Secretary Jacqui Smith and work minister Tony McNulty are being investigated over their claims - but both say they acted within the rules.
WHAT IS THE COMMITTEE ON STANDARDS IN PUBLIC LIFE?
The committee was set up by John Major in 1994, after a series of scandals involving MPs, to advise government on ethical standards
It is funded by the Cabinet Office but independent of government
It has 10 members, approved by the prime minister
Sir Christopher Kelly became chairman in 2008
Ms Smith has apologised for "mistakenly" claiming £10 for two adult films watched by her husband.
Mr Brown's proposal to end the second homes allowance, worth up to £24,000 a year for MPs outside central London, was cautiously welcomed by Mr Cameron and Mr Clegg, but both raised concerns about the idea of replacing it with a flat-rate daily attendance allowance.
The Conservative Party published its own reform plans on Thursday, calling for the second homes allowance to be replaced by a transparent Parliamentary allowance from 1 July.
This could be used to pay only for rent, utility bills, council tax and mortgage interest - subject to a new cap.
All claims would have to published, with receipts, within 28 days, with no MP living within 20 miles of London eligible for the new allowance.
Meanwhile, MPs who co-habit could only claim once.
For the Lib Dems, Mr Clegg has said he would allow MPs to claim taxpayers' money for rent but not to help buy second homes.
'Lack of transparency'
Despite lacking support from the other parties, Downing Street has said the government still plans to table a vote on expenses reform next week, stressing some interim measures were needed pending Sir Christopher's inquiry.
A spokesman said MPs would only be asked to approve the principle of a new system not a specific allowance.
In Parliament, Commons leader Harriet Harman said the proposed system would be transparent since MPs would have to provide "evidence" of attendance at Westminster.
"We are not going to come to a perfect solution," she said. "But it would be good if we could find as much agreement as possible."
The Lib Dems have called for MPs to be allowed to debate proposals other than the flat-rate attendance fee.
Its Commons spokesman David Howarth described Mr Brown's proposal as an "ill-smelling pig in a poke".
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