Labour MP for Great Grimsby Austin Mitchell apologised for wrongly claiming more than £10,000 on his Commons expenses.
The discrepancy in his claims for mortgage repayments on his second home was discovered by Sir Thomas Legg in his recent audit.
Mr Mitchell said he had repaid the money and wanted to announce the "error" before it was exposed in Sir Thomas's repor
t next month.
"I am releasing this information now ahead of whatever announcements Sir Tom Legg makes on claims for repayment by the generality of Members because I have no wish to contest his ruling in my case," he said in a statement.
"I am sorry."
Dozens of MPs are thought to have contested Sir Thomas's demands to make repayments following his audit of all of their claims between 2004 and 2008.
Mr Mitchell, a backbencher, said Sir Thomas had discovered he had been over-paid £10,549 in expenses on his mortgage claims. MPs are only allowed to claim for mortgage interest rather than capital repayments.
"My mortgage is on an interest-only basis but an authorised addition to it in 2006 was, for some reason and certainly not at my request, put by the bank onto a repayment basis," he said.
"I was careless not to recognise this but the regular bank statements gave only a single sum with no distinction between interest and repayment.
"An overpayment occurred and I have paid this back to the Fees Office and changed the mortgage."
