Mr Brown said he did not regret his internet announcement
Prime Minister Gordon Brown has said he does not regret proposing sweeping changes to MPs' expenses, insisting it was the "right thing to do".
He said it was "ridiculous" to suggest dropping a key proposal - replacing the second home allowance with a daily payment for MPs - had been damaging.
Tory leader David Cameron said the "U-turn" meant the plan was now a "farce".
Meanwhile, the Commons Standards Committee has warned against "rushing" into a Commons vote on the issue.
Measures to be debated include stopping MPs in greater London from claiming second home allowances and requiring more details of MPs' earnings outside Parliament to be published.
MPs will also get to debate and vote on a plan to make the Commons responsible for employing staff and also requiring receipts to be submitted for all claims - rather than just those over £25 as at present.
But Mr Brown also said he still expected any new system, which will be looked at by the independent Committee on Standards in Public Life, to address the issues of MPs' attendance at Parliament, transparency and reduced overall costs.
Nick Clegg on efforts to reach a consensus
He said: "As far as what is called the additional costs allowance [second homes allowance] is concerned - everybody now agrees that has got to go and be abolished."
He added: "Far from going backwards we have made enormous progress over the few past weeks."
Mr Brown also said: "I don't regret doing anything I've done on this because it was the right thing to do."
He said he expected the Committee on Standards in Public Life, which had been expected to publish proposals by the end of the year, to produce an "earlier report" - he had already asked them to report back by July.
Mr Brown suggested Commons leader Harriet Harman would come back to MPs with a progress report before the end of the "summer parliamentary session".
But sources close to the committee said it was "unrealistic" to say it should report back by July and that its chairman, Sir Christopher Kelly, would not be "boxed in".
They said Mr Brown's preference for a daily allowance would merely be "one option to consider."
Meanwhile the Commons standards committee - made up of senior MPs - has called for any decisions on expenses to be postponed until after Sir Christopher's committee completes its review.
The cross-party body has tabled its own amendment to Thursday's debate saying the review should not be "pre-empted by decisions of the House of Commons" - saying only an external review would command public support.
Tory MP Sir George Young, the standards committee's chairman, said: "There are real risks with rushing into decisions on Thursday, without having had proper time to consider the issues, which we then have to rewind.
"The unanimous view of the committee was that it was better to wait for the review by the Committee on Standards in Public Life, chaired by Sir Christopher."
A Downing Street spokesman said: "As we have been clear throughout, what we are proposing are interim measures while Sir Christopher Kelly is carrying out his review and that in order to restore public confidence it is important that, where we have agreement on measures that we can act on now, we do so."
Liberal Democrat leader Nick Clegg said the revised debate and vote was "the worst of both worlds" as the most important issue had been "kicked into the long grass".
Mr Cameron said: "What we've seen from the prime minister is a U-turn, followed by a climbdown, and now descending into farce."
Recent revelations about some MPs and ministers' expenses claims have brought the issue back into the spotlight.
Home Secretary Jacqui Smith and work minister Tony McNulty are being investigated over their second homes expenses claims - both say they acted within the rules.
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