Three Plaid Cymru MPs have been found guilty of spending taxpayers' money improperly after taking out adverts which broke parliamentary rules.
The local paper adverts explained the MPs' views on major issues
Elfyn Llwyd, Adam Price and Hywel Williams have been told to repay the cost of the "campaigning" adverts.
The MPs accepted the Commons standards committee ruling but said they acted in good faith when placing the adverts before the Welsh assembly election.
Money for MPs to communicate with constituents had paid for the adverts.
This breached parliamentary rules because the adverts had been in newspapers such as the Daily Post, with circulations beyond the MPs' constituencies.
The standards and privileges committee said the adverts were effectively campaigning.
Elfyn Llwyd's advert appeared in the Daily Post
The committee said the MPs "broke no clear rule of the House" over the timing of the adverts, published in April, just before the Welsh assembly election in May.
But it said it believed "the timing was clearly related to the assembly elections, and any attempt to pretend otherwise is disingenuous". The committee said the MPs should repay the money - about £5,000 each.
Government whip Wayne David said the Plaid MPs had been "found guilty as charged".
He said: "I sincerely hope that Plaid will pay back the taxpayer's money to parliament, and will apologise both to the House of Commons and to the people of Wales.
"I also hope that Plaid Cymru will now submit full and accurate election returns for last May's assembly elections.
"Rather than admit their guilt, they have attempted to defend the indefensible."
Responding to the report on behalf of the three MPs, Plaid parliamentary leader Elfyn Llwyd MP said they accepted the ruling and would "comply fully with it".
But Mr Llwyd said they were "disappointed with the outcome".
He said: " We maintain that we have acted in good faith throughout, and fully in line with the advice that was offered to us by the DFA (Department of Finance and Administration) at the time of the publication of the reports".
Mr Llwyd also highlighted the fact that the report had suggested a need for "further consideration" of the rules on communications allowances.