The husband and wife MPs faced questions about the location of their second home, for which they have claimed tens of thousands of pounds of allowances.

In a report, the Commons Standards and Privileges Committee said: "The Commissioner has dismissed the complaint, having concluded, in the light of his investigation, that 'Ms Cooper and Mr Balls made reasonable decisions on the basis of their own circumstances in declaring their property in Castleford to be their main home'."

The investigation by the Parliamentary Commissioner for Standards, John Lyon, followed a complaint from Tory MP Malcolm Moss. It centred on the Cabinet couple's claims, totalling more than £24,000 in 2007/08, in second homes allowance for their London property.

In a joint statement, Mr Balls and Ms Cooper accused Mr Moss of seeking to make political capital out of the complaint.

"We welcome the Parliamentary Commissioner's decision to dismiss this complaint after a full investigation and his conclusion that we acted fully in accordance with both the letter and the spirit of the rules of the House," they said.

"As the Commissioner's report shows, the allegation made by Conservative MP Malcolm Moss was politically motivated. Malcolm Moss has been open from the start about the fact that he had complained 'because the press was full of stories on the Tory side of expenses'."

The Commissioner said that Mr Balls and Ms Cooper did not, however, spend most of their nights in their Castleford home, which serves as a base for their neighbouring Yorkshire constituencies.

The Green Book of rules on Parliamentary expenses says that an MP's main home is "normally" where they spend more nights.

But Mr Lyon, in a report to the Commons Standards and Privileges Committee, said the rule should not always be rigidly applied.