Russell Brand accused Nigel Farage of being a "pound shop Enoch Powell" as the comedian and the Ukip leader clashed on Question Time.
The My Booky Wook author also warned the Canterbury audience to "watch" Farage because of his stance on immigration.
"There was an economic crash and a lot of money was lost," Brand said.
"His mates in the city farted, Nigel Farage is pointing at the immigrants and the disabled and holding his nose.
"Immigrants are not causing the economic problems.
"I, as much as any of us, enjoy seeing Nigel Farage in a boozer with a fag, laughing off his latest scandals about breast feeding or whatever.
"I enjoy it. But this man is not a cartoon character.
"He ain't Del Boy. He ain't Arthur Daley. He is a pound shop Enoch Powell. We gotta watch him."
But the Ukip leader hit back at the campaigner and pressed him to answer a question from the audience about overcrowding in the UK.
"This is called Question Time this programme," Farage retorted.
"And what happens is members of the audience ask questions and we're expected to answer them.
"You haven't answered this lady's question. Do you think Britain is overcrowded?
"There is a strain on public resources and people's quality of life."
Brand was later criticised by a member of the audience for not attempting to become an MP.
"You are a campaigner...Stand. Stand for parliament. If you're going to campaign, then stand. You've got the media profile for it, do it," the audience member told Brand.
But the film star said he was "scared" to make the move because he might "become one of them".
Brand also apologised for his sexist remarks after calling on the Fire Minister Penny Mordaunt to pay firefighters their pensions – referring to the ongoing dispute between the Fire Brigades Union (FBU) and the government.
"'Pay their pensions then, love," the comedian said.