Nigel Farage has claimed a decisive victory for the Brexit Party in the European Parliament elections could see the end of both Theresa May and Jeremy Corbyn’s leadership, in a “buy one get one free” result.

The prominent Brexiteer rallied his supporters ahead of Thursdays poll, claiming Westminster was "terrified" by the rise of his new outfit in recent weeks.

He described Ms May as the "most duplicitous prime minister in the history" and turned his fire on Tory leadership hopeful Boris Johnson, leading to boos and shouts of "traitor" from the audience.

Organisers estimated 3,000 people attended the rally in London, with speeches from former Tory minister Ann Widdecombe and former Czech prime minister Vaclav Klaus.

Both the Tories and Labour are braced for a Brexit backlash in the upcoming European election, with the Brexit Party regularly topping the polls

A buoyant Mr Farage told the crowds: "If we win big on Thursday, there are a couple or really nice little focuses that will be attached.

"The first is we will quickly get rid of the worst, most duplicitous prime minister in the history of our nation.

"Given the way we are smashing the Labour vote in Wales and in the north of England, you never know a big Brexit win may get rid of Jeremy Corbyn as well.

"Buy one get one free - how about that?"

Yougov poll, by Statista

The former Ukip leader said a good result for his party would put pressure on the government to deliver Brexit by 31 October and bring back the threat of a no deal.

He also warned it would "kill of any prospect" of parliament pursuing a second referendum.

Mr Farage also mocked Mr Johnson for describing the prime minister’s deal as “vassalage” and then voting for it, adding: “You cannot trust the political class in this county."

His intervention came as Ms May's last-ditch attempt to save her Brexit plan looked set to fail as angry Tory MPs deserted her and Labour rebuffed her attempts to win them over.

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In a speech in London, she promised to offer MPs a vote on whether to hold a second referendum in a desperate bid to secure support for her beleaguered Brexit plan.