By Alex Stevenson
Gordon Brown broke Commons rules when he sublet part of his constituency office, parliament's standards watchdog has found.
But the prime minister will not be forced to repeat his apology for the wrongdoing to the Commons because it was inadvertent.
The standards and privileges committee, in its report on the prime minister's conduct, noted "it is clearly dangerous for members of parliament to assume that the rules of other parliamentary assemblies. are the same as those of the House of Commons" but did not call for any further action.
The announcement comes a week before shadow communities and local government secretary Caroline Spelman faces a verdict from the same committee over a complaint made against her.
The committee is believed to be struggling to reach consensus over allegations the Meriden MP's former nanny was paid for secretarial work she did not do.
Today's judgment against the prime minister quashes speculation among Conservative bloggers that a sharper rebuke for Mr Brown might lead to Ms Spelman's case being downplayed in a "gentleman's agreement" between the two parties.
The complaint against Mr Brown, raised by Conservative MP Greg Hands, related to Mr Brown subletting his constituency office in Kirkcaldy to his local party from July 2005 to March 2008.
As he claimed parliamentary allowances for the accommodation this meant he broken Commons rules, but - because staff deducted the claim by the amount received as rent from the sub-tenant - he did not gain financially.
Furthermore Mr Brown was sharing the office with Marilyn Livingstone MSP, whose staff were in charge of the arrangements.
As a result of these factors Sir John Lyon wrote: "I am satisfied that Mr Brown's subletting of the constituency office was an inadvertent breach of the rules.
"It brought no financial benefit to Mr Brown, and once it was identified, Mr Brown moved quickly and effectively to rectify the situation."
The House authorities received greater criticism, however, for not taking "greater care in checking the information they receive from members".