British comedian John Oliver laid waste to Stephen Harper just hours before Canadians lined up at polling booths to choose their next government.

Oliver mocked the Prime Minister for everything from gutting environmental laws, whipping up Islamophobia through the niqab row, and most hilariously of all pilloried the PM for his band's coverage of 'Sweet Caroline,' before appealing to Canada's southern neighbours to care some more.

“I know it's hard for Americans to care about this, but think of it this way. Picture your next-door neighbour. You might not be great friends with her, but you'd be sad if she started dating a complete and utter d***head," he said.

"Well, Canada is America’s next-door neighbor, and Stephen Harper is her d***head boyfriend. You know, the one she won’t split up with despite the fact that he tells her what to wear and makes her listen to his s***ty, s***ty band.”

John Oliver takes aim at Canada

Keeping up his merciless onslaught, Oliver taunted the Canadian government by saying that federal law threatened him with a $5,000 fine and six months in jail, before whipping out a wad of Canadian cash.

"I'm going to get my money's worth," vowed Oliver, who then displayed a person in a beaver costume playing Sweet Caroline, a moose getting a colonoscopy, and Mike Myers on a snowmobile.

However, Oliver pulled no punches with Harper's opponents either, poking fun at both the Liberals and NDP, showing a video of the latter's leader making an attempt at a catchy slogan.

"Healthcare. Childcare. Pharmacare. Mulcair. This is what change looks like," said Mulcair during one rally, only to be dissected by Oliver.

"Ooh, you are not what change looks like. I understand you're talking about your policies but still, change visually does not look like Paul Giamatti's uncle reading a rhyming dictionary," mocked Oliver.

He then took aim at Justin Trudeau, lampooning his 'falling down the stairs trick' as unworthy of a head of state, saying that it was satisfying to see a "man named Justin with a French accent just fall down some stairs. There's something there that's good about it."

He also described Canada's 78-day election campaign - the longest in its history since 1872 - as "adorable."

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