MPs unanimously approved a report by the Standard and Privileges Committee on 6 November 2012, finding that Labour MP Denis MacShane was guilty of submitting false expense claims.
The report recommended that he be suspended from the Commons for 12 months, but Mr MacShane has since resigned from his seat anyway, saying he wanted to "take responsibility" for his mistakes.
Committee chair Kevin Barron said the case was the "gravest" to come before the committee for adjudication, rather than to the courts for prosecution.
The committee found that Mr MacShane had submitted £7,500 of false expense claims, filed between 2005 and 2008.
Mr Barron argued: "The absolute sums are not the issue, it was the manner in which they were claimed, the flagrant disregard for the rules of the House, and the failure to co-operate with the Commissioner's investigations which concerned the committee.
"This was a breach of conduct. There may have been suggestions that members were above the criminal law. I would just like to say that this is not true and it really needs to be addressed."
Leader of the House Andrew Lansley said Mr MacShane's behaviour had been "deeply reprehensive".
It would have "angered many of our constituents and members of this House alike", he said.
"We should expect members of Parliament themselves to set and meet the highest standards of conduct. That they have not is a matter of deep regret and I know we will be determined to demonstrate we will not tolerate such lamentable breaches of those standards."
Shadow leader Angela Eagle said the "sorry episode" reinforced the importance of MPs' serious treatment of the new rules that were established after the 2009 expenses scandal.
But Labour backbencher Michael Connarty said Mr MacShane had fallen victim to "double standards", because Liberal Democrat David Laws, who resigned as chief secretary to the Treasury when he was found "quite clearly guilty" of wrongly claiming thousands of pounds, had since been allowed to return to the government.