MPs' expenses watchdog Ipsa has published information about 20 members of parliament whose expenses it probed - and revealed that in nearly every case, it was partly at fault.
The news will add more pressure on the Independent Parliamentary Standards Authority, which has been roundly criticised by MPs.
They published investigation details relating to political heavyweights such as Tory deputy chairman Michael Fallon, shadow education secretary Stephen Twigg, Boris Johnson's brother Joseph Johnson, Climate minister Greg Barker, and former Labour minister Alan Johnson.
Also named were: David Anderson, Bob Blackman, Ann Coffey, Robert Halfon, Gordon Henderson, Mark Hendrick, Kwasi Kwarteng, Mar Lancaster, Jim McGovern, Ian Mearns, Michael Alun, Angus Robertson, Henry Smith, Ian Swales and Hywel Williams.
The claims were largely related to MPs' expenses for their personal websites. In each case, Ipsa's compliance officer found the organisation was partly at fault or the amount disputed was minor - and the MP had acted fast to correct the claim.
In another investigation, relating to Conservative MP Peter Aldous's claims for accommodation, Ipsa found that they were partly at fault and that he had acknowledged the error and repaid the body.
In September, a report by the influential public accounts committee found the expenses system for MPs is so inefficient that it costs more to process some claims that the value of the claim itself.