Twenty MPs fell foul of expenses rules by claiming for websites which featured party political logos.
Conservative deputy chairman Michael Fallon and former Labour home secretary Alan Johnson are among MPs named by the expenses compliance officer.
Under expenses rules, claims cannot be made for any material "that contains a party political logo or emblem".
Another MP, Peter Aldous, repaid £361 he had claimed for a hotel at a time he was also claiming to rent a property.
The compliance officer for the Independent Parliamentary Standards Authority (Ipsa) said in each case, Ipsa itself was partly to blame for not picking up the problems when claims - which all date back to 2010 - were submitted. He said the watchdog had since "strengthened its validation practices".
No MPs were fined - something that is within the powers of the compliance officer - but all removed the logos or chose to return the money and fund the websites out of their own pockets. Amounts claimed ranged from between about £100 to just over £1,000.
Under the new system, set up following the expenses scandal of 2009, a compliance officer can choose to initiate his own investigations into MPs rather than wait for a complaint to be made.
Nineteen of the 20 cases were initiated by the compliance officer - apparently triggered by an initial complaint from someone about the website of Lib Dem MP Ian Swales.
In several cases party logos appeared on the "links" page of the websites, in two cases they appeared in "favicons" - an image which typically appears in the address bar at the top of the page.
The Conservative MP Henry Smith said he had not even been aware the favicons were on his website, as they were added by the website designer and did not appear on his web browser.
In the case of Mr Aldous, an independent complaint was made about three claims for hotel expenses in September 2010, amounting to £361. At the time he was also claiming to rent a property.
The MP apologised and repaid the money - saying he had stayed in the hotel for a few days while getting a few basic items to make his new flat "habitable" - the compliance officer accepted his explanation that it was a "genuine oversight".
A spokesman for Ipsa said: "We accept the compliance officer's findings and welcome the conclusion that we have strengthened our processes. This follows the National Audit Office's recent report which found that we are safeguarding public money."
Martyn Taylor, previously Ipsa's head of governance, is currently the acting compliance officer - the third person to occupy the post in just over a year.
The first full-time compliance officer, Luke March, resigned suddenly in August, having concluded it was "not the right role for me".
Days earlier he had said he would not publish the names of those under investigation, until his inquiries were complete - despite guidelines saying names should be published when he started looking into a case.
He said MPs were very nervous about expenses investigations following the expenses scandal and weekly meetings with them was like "walking on thin ice".
Mr March told the BBC shortly before he resigned that he had been dealing with a backlog of cases, having only taken over the role in March 2011.
But he said: "One of the things that crops up time and time again is MPs' websites. One of the very detailed rules in place is a website has to be used for parliamentary duties and obviously not for political duties."
In May, it emerged that he had been carrying out "preliminary" investigations into about 40 possible breaches of expenses rules.
Until Tuesday, the only one who had been named was the Lib Dem MP Bob Russell - who named himself during a committee hearing involving Ipsa's chairman. He said at the time he suspected "political opponents" were behind it and it is believed the case was dropped.
He is not among the completed investigations published on Tuesday.