The Prime Minister, campaigning to win a Brexit mandate, has claimed anything other than a Tory victory would mean a “coalition of chaos”.
And the Labour leader, launching a Donald Trump-style insurgency campaign, has vowed to take on the establishment and says he will not “play by the rules” in the election.
Mr Corbyn is also pledging to target the rich, claiming he will “put the interests of the majority first” and stand up for people held by a rigged economic system.
Video:PM says ‘No’ to election debates
The opening salvos from the party leaders came as it emerged that while the Prime Minister is refusing to appear in head-to-head TV debates with her rivals, she may agree to other formats.
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Downing Street is considering proposals from broadcasters, including Sky News, which could see the Prime Minister being interviewed in front of a live studio audience.
Video: PM makes speech after election vote
In her first campaign visit, to a Labour marginal in Bolton, the Prime Minister told an invited audience: “There’s a very clear choice at this election.
“It’s a choice between strong and stable leadership under the Conservatives, or weak and unstable coalition of chaos led by Jeremy Corbyn.”
Video:Where will election leave Labour?
Mr Corbyn insists he will not go into coalition with the Scottish National Party.
Speaking at a Tory marginal in Croydon, the Labour leader signalled that the party’s manifesto will include an assault on the rich.
“Are we going to be a country that gives riches and makes riches for all of us?” he said.
“Or are we going to be a country that works to make the rich even richer? I know which side I’m on, you know which side you’re on.”
Video:Jeremy Corbyn begins campaign in Croydon
In his first major policy speech of the campaign, in central London, Mr Corbyn will say: “Much of the media and establishment are saying this election is a foregone conclusion.
“They think there are rules in politics, which if you don’t follow by doffing your cap to powerful people, accepting that things can’t really change, then you can’t win.
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“But of course those people don’t want us to win. Because when we win, it’s the people, not the powerful, who win. The nurse, the teacher, the small trader, the carer, the builder, the office worker win. We all win.
“They say I don’t play by the rules – their rules. We can’t win, they say, because we don’t play their game. They’re quite right, I don’t. And a Labour Government elected on 8 June won’t play by their rules. ”
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He will add: “These rules have created a cosy cartel which rigs the system in favour of a few powerful and wealthy individuals and corporations. It’s a rigged system set up by the wealth extractors for the wealth extractors.
“But things can, and they will, change. And Labour in this election will be part of a movement of the British people to make that change.
“How dare they crash the economy with their recklessness and greed, and then punish those who had nothing to do with it.
“We will overturn this rigged system. The Conservatives will never do that. Seven years of broken promises show us that: on wages, the deficit, the NHS, our schools, our environment. ”
And attacking top bosses, he will say: “If I were Southern Rail or Philip Green, I’d be worried about a Labour Government.
“Labour is the party that will put the interests of the majority first.
“That’s why we will prove the establishment experts wrong and change the direction of this election – because the British people know that they are the true wealth creators, held back by a system rigged for the wealth extractors.”