AN angry Nicola Sturgeon has said it is “outrageous and unacceptable” for Sky News to exclude her from its offer of a televised party leaders’ debate after ITV did so for its live election head-to-head.

Once Sky announced its proposed line-up for Thursday, November 28, featuring Boris Johnson, Jeremy Corbyn and Jo Swinson, the First Minister took to social media to complain.

She tweeted: “Simply outrageous and unacceptable to exclude @theSNP - the third-largest party in UK. What are the other parties so scared of that they won’t agree to real debate? And why are broadcasters letting downvoters, especially in Scotland?”

Earlier, the SNP leader challenged her Conservative and Labour counterparts to a debate “anytime, anywhere”.

At Westminster, an equally indignant Ms Swinson held a press conference outside the House of Commons, surrounded by Liberal Democrat candidates, to warn that she would take legal action to ensure she took part in the ITV’s leaders’ debate on Tuesday November 19, which is scheduled to feature just the Prime Minister and the Leader of the Opposition.

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"As Liberal Democrats, we will take any action required to make sure that that voice of Remain is represented in those debates. We are taking legal advice and we will pursue legal avenues if ITV do not change their format,” the East Dunbartonshire MP declared.

She decried an “Establishment stitch-up” by the two “tired old parties” at Westminster, arguing it was important that not only millions of Remainers had their voice represented to ensure it was a fair debate but also that girls and young women could see that women were able to be political leaders and prime ministers too.

“Why are they so scared of taking on a girly swot?” Ms Swinson asked in a reference to a quip Mr Johnson made in reference to his Old Etonian predecessor in No 10 David Cameron.

The Lib Dems have argued their leader and not Ms Sturgeon should be a part of the leaders’ debates because Ms Swinson is vying to be PM and heads the biggest Remain party in the UK. The SNP, by contrast, insist that as the third party at Westminster, their leader should – like Nick Clegg in 2010 - be in any televised leaders’ debates.

Some 90 minutes after the Lib Dem leader held her Commons press conference, Sky made its announcement about an offer of a three-way debate.

Ms Swinson retweeted a tweet about the proposed debate and swiftly wrote: "I'm in. Will you show up @BorisJohnson & @jeremycorbyn?"

Asked if Mr Corbyn would take up Sky’s offer, a Labour spokesman said the party would “consider all opportunities to explain our plans to voters and we are talking to the broadcasters about how to achieve this".

A Conservative Party spokesman, meanwhile, pointed out TV debate discussions were "ongoing".

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Earlier, Ms Sturgeon, campaigning in Rutherglen, where she was joined by SNP candidate Margaret Ferrier, said: “My message to Jeremy Corbyn and Boris Johnson is: 'What are you scared of?' I'll debate one of them, I'll debate both of them, anytime, anywhere.”

She declared: “Bring it on, stop running scared of meaningful debate in this election. The people can see you."

The FM warned broadcasters against "going back in time" by only inviting the leaders of the two largest parties to the debate.

"The population, certainly in Scotland, but across the rest of the UK, is moving away from the two-party system; you've got the broadcasters not only sticking to that but actually going back…because in 2010, 2015 and 2017 they had a different approach to that.

"My message to the broadcasters is make sure that you're reflecting politics as it is and not just how you want it to be."

Her Nationalist colleague Hannah Bardell urged broadcasters not to allow Downing Street to shut out other parties from the debates in a “blatant attempt to rig the election in favour of the Westminster Establishment”.

She pointed to a weekend poll by YouGov which said 53 per cent of those polled wanted the SNP to be included in the debates compared to just 10 per cent who supported plans to restrict them to Mr Johnson and Mr Corbyn. In Scotland, the respective numbers were 73 per cent and five per cent.

ITV has said it is already scheduling a separate live debate to include seven party leaders in addition to the head-to-head on November 19.

At the weekend, a spokesman for the broadcaster said: "ITV intends to offer viewers comprehensive and fairly-balanced General Election coverage. This involves a wide range of programming, including a live debate programme in which seven party leaders are invited to take part, as well as a live debate between the Labour and Conservative leaders."

Sky News has said it is sensible to suggest an alternative approach that would allow voters to properly scrutinise a wider range of views and has promised to continue to provide "appropriate coverage" to other parties in broadcasts throughout the election campaign.