THE BBC has been accused of “short-changing” voters in Scotland after it announced its key televised head-to-head debate would be between just Boris Johnson and Jeremy Corbyn.

The Prime Minister said he was looking forward to the clash with the Leader of the Opposition, tweeting: "I can't wait to share with you all our positive vision for Britain!"

But the Liberal Democrats threatened legal action, the SNP insisted it denied democracy while Plaid Cymru denounced the decision as “absolutely disgraceful”.

The debate formats of all three main broadcasters – the BBC, ITV and Sky – mean that there is likely to be no opportunity for Mr Johnson and Nicola Sturgeon to debate with each other head to head.

While the BBC has scheduled a “seven-way” leaders’ debate, this is for "leaders or senior figures from the seven major GB political parties," meaning that it is possible Mr Johnson will not attend. It is thought Scot Michael Gove, the Cabinet Office Minister, could be the Tories’ representative.

A two-hour BBC Question Time event on Friday November 22 in Sheffield will involve all the leaders of the four main parties, including Jo Swinson, but they will be quizzed individually for 30 minutes by audience members.

The BBC’s Johnson-Corbyn clash will take place in Southampton on Friday December 6, just six days before polling day. It will be hosted by journalist Nick Robinson.

ITV have announced the first head-to-head on Tuesday November 19 but again this will just be between Mr Johnson and Mr Corbyn.

Sky’s planned televised leaders’ debate will take place on Thursday November 28 and will not only involve the PM and the Labour leader but also Ms Swinson.

There will be a special BBC Question Time for an audience of under-30s on Monday December 9 but a corporation spokesman said it had not yet been decided who would be quizzed.

A BBC debate involving all the Scottish party leaders will take place on Tuesday December 10 from Glasgow’s Pacific Quay.

BBC Scotland will also air a 30-minute Debate Spin Room show from the venue beforehand with commentators, journalists, politicians and analysts discussing how the debate will be won and lost.

The broadcaster also announced there would be separate televised 30-minute events with Nigel Farage of the Brexit Party and one of the co-leaders of the Greens; either Sian Berry or Jonathan Bartley. This means Mr Farage will have two opportunities to promote his plans during prime time.

However, the BBC’s decision to stage its main head-to-head event between just Mr Johnson and Mr Corbyn sparked a furious reaction from the Lib Dems and the Scottish and Welsh Nationalists.

Ms Swinson took to Twitter to complain, saying: “The BBC are now complicit in another Establishment stitch-up to shut down debate on the most important issue for generations: Brexit."

She went on: "Millions of people voted to Remain in 2016. After three years of chaos, it is shocking that the Liberal Democrats - the strongest party of Remain - are being denied the opportunity to challenge Johnson and Corbyn on Brexit."

The Scot stressed her party would "pursue legal avenues," adding the broadcaster could “not and should not exclude the only woman leader who is able to be the next Prime Minister".

The SNP's Westminster leader Ian Blackford was also indignant, saying the BBC's decision to exclude his party from a key televised election debate was "senseless" and defied democracy.

He added: "This is the most important election in living memory but the BBC has made the decision to short-change voters in Scotland, and across the UK, by restricting the focus of these debates to just two parties."

Plaid Cymru denounced the decision as "absolutely disgraceful" with the party's candidate for the Carmarthen East and Dinefwr seat Jonathan Edwards adding: "Whether we're talking about a blue Brexit or a red one, both Johnson and Corbyn are prepared to throw Wales under the bus."

Ms Swinson has already complained and threatened legal action over ITV’s decision to exclude her from its televised head-to-head while Ms Sturgeon has made a similar threat against Sky whose key debate excludes her.

Televised General Election debates started in 2010, with Gordon Brown, David Cameron and Nick Clegg clashing in three debates.

In subsequent elections, the formats have been different and have involved battles between the broadcasters and party leaderships over who should be invited to debate whom.

In 2017, the then PM Theresa May refused to take part in a seven-way debate on the BBC, sending her Home Secretary Amber Rudd instead.