Tony McNulty, the Employment Minister, is to be investigated by a Commons watchdog over £60,000 he claimed as a "second home allowance" for the house in which his parents live.

John Lyon, the Parliamentary Commissioner for Standards, has agreed to follow up on a complaint over Mr McNulty by a Conservative MP.

Mr McNulty started claiming allowances for the house in his Harrow constituency in northwest London in 2001 and continued to do so until January this year even though he moved out in 2002 after getting married for the second time.

Since then he has lived in Hammersmith, which is just nine miles from Harrow.

Mr McNulty insists that he has broken no rules. He says that he has continued to use the house, which he owns, two or three days per week while working in the constituency, and slept there at weekends when he first entered Parliament.

A spokeswoman for the Commissioner’s office confirmed he had accepted a complaint against Mr McNulty, but added that he had rejected one made against Labour MP Nigel Griffiths, who reportedly cheated on his wife during a romp in the Commons on Rembrance Day last year.

A formal complaint about Mr McNulty’s Additional Costs Allowance (ACA) claim was made to the Commissioner by Greg Hands, the Tory MP for Hammersmith.

The ACA allows MPs with constituencies outside inner London to claim up to £24,000 to cover the cost of staying overnight away from their main home for the purpose of performing parliamentary duties.

The investigation comes as another watchdog was preparing to launch a comprehensive review of MPs’ pay and perks. Sir Christopher Kelly, who chairs the Committee on Standards in Public Life, said it would begin later this year but not report until after the next general election, expected in 2010.

The exact remit has not yet been revealed, but Gordon Brown has urged the committee to include not just pay and allowances but also the question of MPs’ outside interests and second jobs.

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