THE SNP and Liberal Democrats have insisted their party leaders must be part of any televised UK election debates as ITV announced the first live head-to-head between Boris Johnson and Jeremy Corbyn.

The leaders of the two main UK parties will confront each other on Tuesday November 19 with Julie Etchingham as the moderator.

Last night, a Lib Dem source denounced the Johnson-Corbyn face-off as a "cosy stitch-up between the two Establishment party leaders".

Sources in both the SNP and Lib Dems complained about the prospect of Nicola Sturgeon and Jo Swinson being “frozen out” of what are likely to be the most watched set-piece events of the entire campaign.

“Absolutely we should be there; we are the third party at Westminster and should be treated accordingly,” Ian Blackford, the Nationalist leader in the House of Commons, told The Herald.

An SNP colleague echoed the point, saying: “We are the third party at Westminster and deserve to be on the UK platform. It would be scandalous to keep us out.”

But a Lib Dem source claimed Ms Swinson should be part of a leaders’ debate because she was one of “three people putting themselves forward as prime minister” but Ms Sturgeon should not. “The SNP don’t have a candidate to be PM; plus, they are not standing across the whole of the UK”.

The country’s main broadcasters, the BBC, ITV, Sky News and Channel 4 are all now competing for the right to host what could be a number of set-piece events during the campaign.

It is thought the Tories and Labour both just want a straightforward format between their respective party leaders to crystallise the election to a choice between the two.

They are concerned that Jo Swinson and Ms Sturgeon could perform well and take votes from them from Remain supporters.

A senior Labour source noted: “There are only two possible people who can be prime minister at the end of this election campaign and those two people should have a head-to-head debate.”

Talks between the parties and the broadcasters are said to be “on-going” with a number of possibilities being discussed, including a seven-way UK debate, involving all the leaders of the main and minor parties represented at Westminster.

Last night after ITV made the announcement of the first televised leader’s debate, Jeremy Corbyn took to social media to welcome it.

“This is a once-in-a-generation election. So, it's welcome that Boris Johnson has accepted our challenge of a head-to-head TV debate. The choice could not be clearer: Boris Johnson's Conservatives protecting the privileged few or a Labour government on the side of the many.”

The Prime Minister also took to Twitter to comment, saying: "Looking forward to making the positive case to the country that we should #GetBrexitDone & deliver on the people's priorities - #OurNHS, schools, tackling crime & the cost of living."

But a Lib Dem source told The Herald: "This is a cosy stitch-up between the two Establishment party leaders to try to shut out the woman leader of the strongest party of Remain. They're running scared but we aren't going to let them get away with it."

Mr Johnson was accused of running scarred from TV debates by rival Jeremy Hunt during the race to take over the Tory Party after the departure of Theresa May.

Mr Johnson did take part in two one-on-one debates during the battle for the Tory crown but not before Mr Hunt and others placed him under great pressure to do so.

ITV Press Centre made the announcement on Twitter and said details of further multi-party debates would be released in due course.

In the 2017 election, Conservative HQ decided to keep Mrs May well away from the televised debates altogether, which was later regarded, even by senior Tories, as a major mistake as it reinforced the view that she was being protected from public scrutiny.