BORIS Johnson and Jeremy Corbyn are set to go head-to-head in the first televised debate of the General Election campaign.

The two leaders will face off in an hour-long encounter screened live on ITV this evening.

The way was cleared for the debate to go ahead after the High Court in London rejected a legal challenge by the Liberal Democrats and the SNP over the exclusion of their leaders.

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With Labour trailing in the opinion polls, Mr Corbyn goes into the event - staged at studios in MediaCityUK, Salford - hoping for an opportunity to make up ground on the Conservatives.

In contrast, Mr Johnson, who was criticised for his reluctance to debate directly with his rivals in the Tory leadership election, will be seeking to avoid any misstep which hands ammunition to his opponents.

Ahead of their encounter, Mr Johnson sought to put pressure on Mr Corbyn with an open letter calling on him to say which way he would recommend people should vote in Labour's proposed second EU referendum.

The Labour leader has come under fire over his refusal to say which way he would vote, even though other senior figures including shadow chancellor John McDonnell and shadow foreign secretary Emily Thornberry have made clear they would back Remain.

The Lib Dems and the SNP, meanwhile, remain angry at the exclusion of Jo Swinson and Ms Sturgeon from the televised showdown.

The two parties contested ITV's decision at a hearing in London on Monday, arguing it was unlawful because it breached impartiality rules.

But two leading judges ruled the decision was not open to challenge in the courts and that the parties' only recourse was to complain to the regulator, Ofcom.

Following the ruling, Lib Dem president Baroness Brinton called for televised debates between party leaders to be framed in stronger legislation.

"Our democracy should not be in the hands of invisible corporate structures and arrangements for such debates should always be accessible and transparent," she said.

"We will not set our principles aside, we will continue this fight. Not just for this General Election, but for our future democracy too."

The SNP's leader in Westminster, Ian Blackford, said: "The result of the decision to exclude the SNP is to discriminate against Scottish voters and to effectively treat them as second-class citizens.

"That is, quite simply, a democratic disgrace and the fact that election law and broadcasting codes allow such gross unfairness is unacceptable."

ITV said in a statement: "We welcome the court's decision and will continue with our comprehensive election coverage as planned."

Tonight's debate will be hosted by Julie Etchingham and will be broadcast live on ITV1 from 8pm.

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Ms Swinson is due to take part in a three-way debate with Mr Johnson and Mr Corbyn hosted by Sky on Thursday, November 28.

The following day, the BBC will host a seven-way debate in Cardiff between leaders or senior figures from the seven major GB political parties.

The BBC will then host a "prime ministerial debate" on Friday, December 6, from Southampton between Mr Corbyn and Mr Johnson.