Labour MP David Chaytor has been suspended from the Parliamentary Labour Party pending a watchdog investigation into his expenses, Downing Street announced.
Chief Whip Nick Brown took the decision after speaking to Mr Chaytor about a £13,000 claim, which he has said he will repay, for mortgage interest on a loan which had already been paid off.
The Bury North MP referred the matter to the Parliamentary Commissioner for Standards himself after disclosures about the payments in The Daily Telegraph.
He blamed "an unforgivable error in my accounting procedures for which I apologise unreservedly" for the claim.
A Downing Street spokesman said: "After speaking to David Chaytor this morning, the chief whip has suspended him from the privilege of membership of the Parliamentary Labour Party pending further investigations by the Parliamentary Commissioner for Standards.
"Mr Chaytor chose to refer his own claim to the Standards Commissioner himself."
The suspension should not be seen as a presumption of guilt, he insisted.
Mr Chaytor, who was flying back into the UK this morning after a publicly-funded fact-finding trip to the US, is the second Labour MP to be suspended over such claims.
Former minister Elliot Morley suffered the same fate earlier this week after also referring his case - which involved £16,000 claimed against a paid-off loan - to the Commissioner John Lyon.
