The SNP has mounted a legal challenge against broadcaster ITV over its exclusion of Nicola Sturgeon from a proposed general election debate.

The channel is planning a head-to-head debate between Boris Johnson and Jeremy Corbyn next week but has come under pressure to include other party leaders.

Liberal Democrat leader Jo Swinson will also launch legal action against ITV over her own exclusion from the debate on Monday.

The SNP said it hopes its own challenge is heard "in parallel" with the Lib Dems' but accused Swinson of a "self-centred approach".

Sturgeon's party has also complained about a three-way debate proposed by Sky News between Johnson, Corbyn and Swinson, despite the SNP having more Westminster seats than the Lib Dems.

Launching the action against ITV, the SNP leader said: "This election may be the most important of our lifetimes.

"It is quite simply unacceptable for the SNP and other parties to be cut out of proposed leaders' debates by broadcasters.

"This is fundamentally unfair and it fails to recognise that the UK is no longer a two-party state.

"And in Scotland, this would not be a debate between the two leading parties - instead it would ignore the country's largest party, which according to the latest polls is also on track to win the third largest number of seats UK wide.

"By contrast, the latest polls show Labour in fourth place in Scotland.

"Crucially by the time the second debate with all party representation takes place, many voters will already have cast their postal ballots, meaning this debate gives Labour and the Tories an inbuilt and unfair advantage."

She added: "We are asking that this legal challenge be heard on Monday in parallel with that taken by the Liberal Democrats.

"But unlike their self-centred approach, we will be arguing not just for the SNP but for other parties to have a place in this debate as well, just as was the case in the ITV leaders' debate of 2015."