A formal complaint has been made about £90,000 of expenses claimed by the Conservative culture secretary, Maria Miller.
Labour MP John Mann has complained that Miller’s parents lived in a property designated as her second home whilst she was also claiming parliamentary allowances to cover the costs of the rent.
Mann raised the issue with the Parliamentary Commissioner for Standards, the body charged with investigating MP's financial interests.
Miller has insisted that the issue should not overshadow Tuesday's announcement on the Church and marriage
The period under question is from her appointment as an MP in 2005 to the exposure of the MPs' expenses scandal in 2009.
If true it would mean that Miller's parents had essentially been living rent free at the taxpayers expense.
The culture secretary told Sky News: "My expenses are absolutely in order. They've been audited twice."
Mann, however, claims the living arrangements are "identical to those of [former Labour MP] Tony McNulty who allowed his parents to live in his second home rent free."
An investigation by the Committee on Standards and Privileges in the wake of the expenses scandal found McNulty had broken the rules on expenses.
McNulty subsequently lost his Harrow East seat as a result.
Mann said: "It was a dreadful scandal in 2009 when the corrupt expenses claims were first exposed and it remains a scandal that some of our MPs have still not put their houses in order and voluntarily paid back monies they should not have claimed.
"When this failure occurs its only right that a complaint should go to the Commissioner for Standards.
"The public wants the best from us and it looks as if we still have a way to go before we achieve that."
A spokesman for the culture secretary said she had done nothing wrong: "Mrs Miller's elderly parents have lived with her family for nearly two decades, an arrangement that has been in place long before she was elected as an MP seven years ago. They are dependents under Ipsa rules."