A bid by Ukip to try to woo opposition councillors backfired - after the party failed to pay enough postage on letters aimed at swelling its ranks.
Some members of Canterbury City Council in Kent received cards via the Royal Mail saying letters with not enough stamps on them were being held.
Conservative councillor Darren Ellis was one of those who paid £1.20 to the collect the letter, and he "burst out laughing" when he found out it was from Ukip.
The letter, headed "In Confidence", went on to invite him to get in touch as Ukip starts assembling its team of candidates on the city council next May.
Mr Ellis said: "I got home from work and had a card from the Royal Mail saying that the sender hadn't paid enough postage, and I would have to pay £1.20.
"I thought it might be from a local resident so I paid the £1.20, opened it up and it was from Ukip's local chairman asking if I would join them for the next election.
"I just burst out laughing. I wouldn't consider joining Ukip in a million years. Their views are far to the right of any that I have.
"I understand that three or four other councillors received these Royal Mail cards as well."
Ex-Conservative David Hirst, now Ukip's leader on the city council, said it was "standard practice" to send such letters, but admitted volunteers had failed to pay enough postage.
He said: "We did cock it up because the volunteers that sent the letters out were living in the past and didn't put a big enough stamp on them.
"For that we apologise but volunteers are volunteers." He said the local Ukip party had received "sufficient interest" from opposition councillors about joining the party.