All three of the head-to-head debates will be against Labour leader Jeremy Corbyn, with only the UK's two major political parties to feature.

The TV debates in the pipeline

An ITV debate early in the campaign would be moderated by Julie Etchingham in front of a studio audience, while the BBC has plans for a Question Time style event.

Boris Johnson (left) does not want to enter a TV debate with Nicola Sturgeon

Nicola Sturgeon challenges Boris Johnson to live TV debate on independence

There would also be one-on-one interviews with BBC host Andrew Neil.

A third bid is being considered by Sky News.

But none of the debates are expected to feature either SNP leader and Scottish First Minister Nicola Sturgeon or Liberal Democrats leader and East Dunbartonshire MP Jo Swinson.

Which Tory would debate against the SNP?

The Prime Minister is expected to reject calls for him to take part in a debate with all the other opposition leaders amid concerns the discussion would dissolve into a "slanging match".

One of four Conservative candidates is likely to be chosen for any leadership debates involving the SNP or the Lib Dems - either Michael Gove, Priti Patel, Sajid Javid or Rishi Sunak.

Ms Sturgeon previously challenged Mr Johnson to a TV debate on Scottish independence during the Tory leader's first visit to Scotland as Prime Minister in July.

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

Corbyn wants to go head-to-head

On Wednesday, Mr Johnson dodged a question from Ms Swinson when she challenged him for a discussion.

Mr Corbyn's spokesman said: "As we demanded of Theresa May and she refused to agree, we would challenge Boris Johnson to agree today to head-to-head TV debates in this campaign."

But when asked about a three-way discussion with Ms Swinson, the spokesman replied: "We are in discussion with the broadcasters.

"But there are only two people who can be prime minister at the end of this campaign and I think the British public have a clear right to see them debate head-to-head on TV and hear their cases."

Swinson lays down the challenge

Ms Swinson challenged the PM in the Commons so they can be scrutinised in the run-up to a general election, which is widely-expected to get the go-ahead for 12 December.

She told MPs that voters "deserve better than a choice between the two tired old parties", adding: "So will the Prime Minister commit today to take part in those three-way debates or is he going to run scared?"

Mr Johnson replied: "What the people of this country want is their promises kept.

"I'm not disposed to believe in the promises of the Liberal Democrats when their leaflets in London say they want to revoke the result of the referendum and their leaflets in the south-west of the country don't mention Brexit at all.

"That's the bunch of hypocrites, the lot of them, they stand for nothing but a policy of dither and delay and indecision."

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.

General election 2019: SNP set to be snubbed in plans for three TV debates