Stuart Culllimore is said to be very upset over the attack
Liberal Democrats have apologised after a campaign leaflet was sent out which uses a swear word to describe a Cornish nationalist candidate.
The paperwork was distributed on behalf of Anna Pascoe, Lib Dem candidate for Cornwall Council elections on 4 June.
It calls Mebyon Kernow candidate Stuart Cullimore a "greasy-haired twat". He is considering what action to take.
The Lib Dems are investigating how about 40 of the leaflets were printed and distributed around Camborne.
Dick Cole, leader of Mebyon Kernow, which wants self-government for Cornwall, said the attack was "totally unacceptable".
This is not good for politics in general or for politics in Cornwall
Dick Cole, leader of Mebyon Kernow
He said Mr Cullimore, who declined to comment, was "very upset and offended".
He said: "We have accepted the apology, but we are pretty angry and concerned how this kind of thing can come out of an official Lib Dem office and be distributed during an election period.
"This is not good for politics in general or for politics in Cornwall."
Ms Pascoe's agent, Joe Taylor, said it was not an authorised leaflet, but "some kind of prank that's back-fired".
He said: "I am absolutely outraged about this myself. What's particularly distressing is that we took the decision to fight a positive campaign."
He said he had put out a similar leaflet, of which about 1,700 were printed and checked.
"We think about 40 offending leaflets were distributed by one of our volunteers.
"It's a small but extremely busy office. People are coming and going all the time."
The other candidates running for the Camborne South ward are: Jacqueline Harding - Labour, John Herd - Conservatives, John Woodward - Independent.