More than £290,000 was spent unlawfully by two community councils in Wales, the public spending watchdog has said.
Wales auditor general Adrian Crompton said Buckley Town Council in Flintshire broke its own rules when it spent nearly £270,000 on cleaning contracts and appointing a town centre manager.
Mumbles Community Council in Swansea broke financial rules when it overspent by £21,400 on planning consultants.
Such cases "undermine public trust", Mr Crompton said.
His two reports call for the councils to review their rules, known as standing orders, to remove any ambiguity, and urge them to reconsider the processes they use to buy good and services.
"This year alone I have had to issue twelve reports in the public interest, which highlight serious weaknesses in the financial management and governance and town and community councils in Wales," Mr Crompton said.
"This undermines public trust and can lead to a waste of public money.
"I call on all town and Community councils to take heed and learn from the important lessons within these reports so that communities in Wales get the services and the assurance they rightly deserve."
The more than 730 town and community councils in Wales are mostly funded from a precept added to council tax bills, but they can also charge fees for some services and sell land.
Some are only responsible for the upkeep of town and village halls, but others also look after footpaths, cemeteries, parks and clean streets.