Lord Mandelson believes more MPs will be forced to quit
Some MPs have been too "hastily" condemned over their expenses, Lord Mandelson has said.
The business secretary called for those facing allegations to be "given the chance to justify their actions".
He made his comments as Liberal Democrat leader Nick Clegg said the police should be called in where MPs are accused of defrauding taxpayers.
Both Labour and the Tories have set up internal panels to scrutinise claims and rule on their MPs' futures.
But Mr Clegg, who has seen some of his own MPs come under scrutiny following revelations in the Daily Telegraph, said MPs who have done wrong should be sacked instantly.
He said: "First MPs make own rules, then they exploit their own rules, now they want to be paid for breaking their own rules. People should have power to sack their MP and sack them now."
He said the public also wanted to see the police called in where there was a suspicion of fraud.
Asked on BBC Radio 5 Live whether he would personally contact the police, Mr Clegg said: "I am not going to start publicly saying that I'm going to start shopping people to the police but I think they should be in the hands of the police because fraud is fraud.
Nick Clegg on "shopping" fraudulent MPs
"I travel round the country all the time, people say to me the same thing, 'if we did this at work we'd be either be sent to the police or we'd be out on our ear'.
"And so I think people quite rightly want to see the police involved if there is real criminal fraud and real intent to defraud the taxpayer."
Lord Mandelson said he believed more MPs would be forced to step down by the scandal but he said some had been dealt with too rapidly.
He told BBC News: "People have reached too hasty a judgement about individual MPs.
"In other cases, there is an acceptance by those members of Parliament that they have made errors of judgement and they have made amends and taken decisions accordingly and I think we are going to see a few more MPs in that category."
The Telegraph has been accused by some MPs of dragging democracy down, actually we are raising it up out of the gutter
Andrew Pierce Daily Telegraph
Meanwhile Andrew Pierce, of the Daily Telegraph, has been defending the newspaper's coverage of events, after Julie Kirkbride said she was stepping down after a "barrage of distorted press stories".
He told the BBC there had been "no witch hunt against Julie Kirkbride" - she had gone because of voters' anger in her constituency.
He added that some MPs were standing down and leaders were now committed to reform.
"That's got to be a good thing for democracy," he said.
"The Telegraph has been accused by some MPs of dragging democracy down, actually we are raising it up out of the gutter, where some MPs, sadly, have dragged it down to.
"We are going to get a better Speaker, we are going to get a more transparent expenses system, all three political leaders are absolutely committed to genuine reform in the public glare."
"This is the most important public interest story I would say affecting voters and people in Britain, in decades."
Conservative MP Bill Cash is the latest politician to come under the spotlight after the Telegraph revealed he claimed for rent on a "second home" owned by his daughter. He insists he has done nothing wrong and said he does not intend to stand down.
Labour MP Elliot Morley, who could face a police probe after claiming £16,000 for a mortgage that did not exist, is also facing pressure to step down and is due to meet party officials in his Scunthorpe constituency later.
It comes after Labour's Margaret Moran and Conservative Julie Kirkbride became the latest MPs to stand down over expenses revelations on Thursday.
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