All overpayments of allowances to MPs must be paid back, Labour's Leader of the Commons Harriet Harman said today.
Ms Harman said that the repayment of any claims which were not within the rules was a necessary part of reforms to clean up Parliament which should be in place before the next general election.
Voters in the poll expected next spring will be casting ballots for a more transparent and better regulated House, where those who broke expenses rules will have been punished, according to the Commons leader.
In a speech to the Centre for Public Policy Seminars think-tank in London this morning, Ms Harman said it was "a critical time for parliamentary democracy in this country".
"Our Parliament has suffered much self-inflicted injury, and we all recognise that it is imperative that we make every effort to rebuild trust in modern democratic Britain - not just for the sake of our politicians but for the sake of our citizens who need and are entitled to an effective democracy in which they can trust," said Ms Harman.
The Committee on Standards in Public Life is due to report this autumn with recommendations for a fairer and more robust allowances system.
Those rules will be overseen by the new Independent Parliamentary Standards Authority (IPSA), which will come into being later this year.
But Ms Harman added: "It is not enough for the claims in the future to be clear, transparent and robustly audited.
"We have to deal with the past in a way that commands public confidence. It is not enough for past over-claims to be to be identified and exposed to public scrutiny. They need to be paid back.
"When social security benefits are overpaid, even where it is simply a mistake, they have to be paid back. The same principle must apply to MPs.
"If they were not fully within the rules as they obtained at the time, allowance payments must be paid back."
Sir Thomas Legg, a former auditor at the Commons, is scrutinising all expenses claims from the past five years, and is expected to deliver his findings soon. The IPSA will have the power to deduct past overpayments from members' future claims, Ms Harman said.
She pointed out that reforms were also being considered to strengthen the role of backbenchers in holding the Government to account.
And she stressed that more women are needed in the chamber as a part of the drive to increase diversity.
"Though the House of Commons is much more representative of our diverse ethnic communities, and though women are better represented now than they were when I first entered Parliament in 1982, there is still a long way to go," she added.Reuse content