By Alex Stevenson
Justice secretary Jack Straw failed to register £3,000 donated to him in 2004 despite being prompted to do so, it has emerged.
MPs on the standards and privileges committee said they were "surprised and disappointed" that a senior Cabinet minister would make such a mistake, but are not recommending Mr Straw be forced to apologise to the Commons.
Their report said Mr Straw had already "apologised unreservedly" over the donation, which took the form of sponsorship of an event celebrating Mr Straw's 25th anniversary as an MP in 2004.
Downing Street said the prime minister had "full confidence" in Mr Straw, who was doing an "excellent job" at the Ministry of Justice.
Conservative MP Ben Wallace wrote to Mr Straw calling on him to register the donation by Cantaxx Energy Ventures in October 2006. Mr Straw failed to do so.
It was because of this mistake that the commissioner decided to refer the matter to the standards committee.
"Mr Straw's failure to register a donation made to him in 2004 was a clear, albeit inadvertent, breach of the rules of the House," its report stated.
"This case should. serve as a reminder to all members - and particularly to ministers and to frontbenchers - of the need to ensure their register entries are kept up-to-date at all times."
Mr Straw is not the first government minister to be found to have broken Commons rules today.
Former work and pensions secretary Peter Hain was found to have been guilty of "serious" and "substantial" breaches of the code after failing to register over £100,000 of donations to his unsuccessful campaign for the Labour party's deputy leadership.