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Politicians have been told to pay back thousands of pounds they have already spent in the latest part of a big row about their payments.
MPs get paid for doing their job, but also get extra cash for things they need to be able to do it properly.
The extra money is called expenses, and a national newspaper has been printing details of what MPs wanted it for.
Lots of the items - like new toilet seats or flash furniture - have proved to be very embarrassing for the MPs.
The money politicians are paid - both in wages and expenses - comes from the taxes people like your mum and dad pay the government.
BBC political editor explains expenses
Now politicians from all political parties are trying to say sorry for some of the things they've been spending money on, even though they haven't broken any rules.
Prime Minister Gordon Brown said: "I want to apologise on behalf of politicians, on behalf of all parties, for what has happened in the events of the last few days.''
Leader of the Conservatives David Cameron admitted the public had been let down.
"Politicians have done things that are unethical and wrong," he said. "This is public money. Taxpayers money. As MPs, we should never forget that.''
And Liberal Democrats leader Nick Clegg said he would come down "like a ton of bricks" on any MP who tries to con taxpayers.
Prime Minister Gordon Brown says all receipts will be checked
The Daily Telegraph has been printing the details of what the politicians have spent their expenses on.
Examples of some of the things Labour Party and Conservative politicians have been buying have already been published, and on Wednesday it was the Liberal Democrats' turn.
Prime Minister Gordon Brown says receipts on MPs expenses over the past four years will now be checked to make sure every claim is within the rules.
Another idea is to change the rules so politicians can't claim for so many things in the future.