Ed Miliband has challenged Russell Brand over his view that voting is "pointless" in a video interview conducted by the campaigning comedian.
Taken to task by Brand about public disillusionment with politics, the Labour leader replied: "You implied... no change happened. That's just wrong."
Prime Minister David Cameron called Mr Miliband's meeting with Brand a "joke".
But Mr Miliband said the interview was a way to engage with millions of people not usually interested in politics.
His appearance received a mixed reaction on social media, with some complaining it was little more than an ego trip for the comedian and others mocking the Labour leader's accent and choice of language.
In the 15-minute interview posted on his YouTube Channel, The Trews, Brand challenged Mr Miliband over the ability of politicians to address inequality and tax avoidance.
"The reason I have never voted in my life is that I think it does not matter," Brand, who has encouraged people not to vote and advocated a political revolution through action, told the Labour leader.
"We all got excited by Tony Blair, we all got excited by Barack Obama and what happened."
In response, Mr Miliband said he was the man to tackle powerful interests but downplayed expectations about how quickly this would happen.
"This is important. I am not looking for euphoria. I know that might sound a bit weird... You don't want politicians saying 'vote for me and on day one the world is transformed'. It ain't going to be like that. Change is hard. Change takes time."
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The Labour leader said voting was an essential part of the political process. People's votes had been responsible for major social and economic transformations, including the birth of the NHS, equal-pay legislation and gay marriage, he said.
"Without politics and without government, that change does not happen. That is what happens in a democratic society," Mr Miliband said.
The two men were filmed discussing a range of issues in the comedian's east London home, with Brand pressing the Labour leader about why no bankers had gone to prison for market-rigging.
"Of course, if there's fraud committed by bankers that should happen. But there's a bigger issue than that, which is how you have a banking system that works for ordinary small businesses... for customers who need the help," said the Labour leader.
Challenged by Brand over the difference between the proportion of an average person's income taken in tax, and the percentage of profits handed over by companies like internet giant Amazon, Mr Miliband said "of course" politicians had the power to act.
"It doesn't mean it's easy in a world where capital and companies are mobile. You have to have a government which is willing to say 'there's something wrong with this and we're going to deal with it'."
'Pint on head'
There was little of Brand's comedic touch about the video.
However, when discussing a perceived inability on the part of the public to distinguish between politicians, Brand referred to UKIP leader Nigel Farage's campaigning style in saying: "When someone with a pint on their head turns up it seems like a valid and interesting alternative."
"I'm not sure I'd look so good with a pint on my head," Mr Miliband replied.
Brand ends the video by addressing the camera to say he "learned a lot about Labour, a lot about Ed Miliband" and that he found it an "interesting experience".
He added that it "said a lot" that the Labour leader was prepared to be interviewed by him.
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