Former Labour minister Denis MacShane has quit as an MP after he wrongfully claimed at least £7,500 in expenses.
A Parliamentary committee found he had submitted 19 false invoices which were "plainly intended to deceive" Parliament's expenses authority.
The committee said it was the "gravest case" which has come to them for adjudication.
Mr MacShane, who has has repaid the money, said he wanted to take responsibility for his mistakes.
A by-election is now expected in his Rotherham constituency, where he has been an MP since 1994.
Conservative MP Philip Davies has written to the Metropolitan Police, who closed an inquiry into Mr MacShane's expenses in July, asking them to reopen it in light of the report - which he said contained new evidence.
The Met said it would now consider the contents of the report in due course.
The committee's report described Mr MacShane's false claims as "far from what would be acceptable in any walk of life" and "fell far below the standards of integrity and probity expected of every member of the House".
It suggested of the £12,900 claimed through false invoices, it was likely around £7,500 was "outside the rules", although Mr MacShane has apologised and repaid the entire £12,900.
The committee also criticised the MP for failing to co-operate with the inquiry.
The false invoices related to work Mr MacShane carried out in Europe, an area for which he previously had ministerial responsibility.
Between 2004 and 2008, he submitted 19 invoices totalling £12,900 for "research and translation" work carried out by the European Policy Institute.
But the Parliamentary Commissioner for Standards found the claims also covered travel, subsistence, hospitality and the purchase of books and other publications and were broad estimates of what the MP judged he had spent, rather than receipted items.
He also found that the European Policy Institute, in the way it was presented on the invoice - with a general manager and directors - did not exist.
The organisation was a "loose network", with no office, no salaried staff and with a bank account controlled by Mr MacShane himself.
And the signature on the invoices purporting to be from the institute' s general manager was, in fact, from Mr MacShane.
The commissioner said: "The sum claimed was not a sum determined by the general manager of the EPI... it was the sum of money entered on his computer by Mr MacShane himself.
"In effect, he was sending the invoice to himself and writing his own cheque."
The "real mischief" of Mr MacShane's actions, the commissioner added, was submitting invoices that bypassed the "checks and controls" of the House and "enabled Mr MacShane to spend public money as he thought fit".
'No personal gain'
Mr MacShane was also criticised for "excessive" claims for computer equipment, which MPs are allowed to claim for to support their parliamentary work.
In one instance the commissioner found he had allowed an intern to take a publicly-funded laptop away at the end of their internship, and bought a new one for his next intern. He also claimed for the same computer twice.
In a statement, Mr MacShane said: "I have been overwhelmed by messages of support for my work as an MP on a range of issues but I accept that my parliamentary career is over.
"I appreciate the committee's ruling that I made no personal gain and I regret my foolishness in the manner I chose to be reimbursed for work including working as the prime minister's personal envoy in Europe.
"I want to thank the people of Rotherham for allowing me to serve as their MP and the Labour Party for allowing me over the years to fight for the causes I believe in.
"I love the House of Commons and I hope by resigning I can serve by showing that MPs must take responsibility for their mistakes and accept the consequences of being in breach of the House rules."