The demand for a second independence referendum next year will be at the centre of the SNP’s campaign at a forthcoming snap election, Nicola Sturgeon has said.

The leader of the SNP made the comment as she set out why her party was backing a new poll on December 9, arguing it would put Boris Johnson in a weak position given his “do or die” promise that the UK would be leaving the EU on October 31.

Taking to Twitter, the First Minister wrote: “Firstly, we have to ask ourselves what the alternative is. Doing nothing allows Johnson to get his bad deal through (with Lab support) or, even worse, run down clock to end January when No Deal becomes a real risk all over again ... For all his bluster, Johnson would much prefer to fight an election with Brexit already ‘delivered’. An election now would instead force him to explain his failure to keep his October 31 ‘do or die’ promise and also defend his bad deal.”

She added: “Finally, all of this Brexit chaos is being imposed on Scotland against our will. To stop this ever happening again, we need to be independent – which is why the demand for #indyref2020 will be at heart of @theSNP campaign.”

READ MORE: MPs to vote on December election as EU decides Brexit extension length 

Boris Johnson has said in the past he would prefer to be “dead in a ditch” than miss the October 31 deadline.

The PM will likely fail to secure “super majority” support for a December election on Monday – but knows he will require 100 fewer MPs to grant the same request just 24 hours later.

Labour’s lack of support for the proposal means it is likely to be defeated when voted upon on Monday evening.

Mr Johnson has already had two requests for an election refused, but the Liberal Democrats and Scottish National Party have offered Mr Johnson a way out of the deadlock.

Lib Dem leader Jo Swinson and the SNP’s Westminster leader Ian Blackford have put forward a tightly-drafted Bill that would grant an election on December 9 – three days earlier than the PM’s suggested polling date – as long as the European Union grant an extension until January 31.

Number 10 hinted it could back the opposition parties' proposal for a Bill, requiring only a simple Commons majority, that proposes an election on December 9 should Labour decline to back the Prime Minister's push for a General Election today.

Ian Blackford told the Sunday National: “What [Johnson] is trying to do is squeeze through his deal in the next couple of weeks, so that we end up in transition, we are out of Europe and then he has an election. That is simply not acceptable.

READ MORE: EU preparing to sign off on Brexit extension, according to leaked paper

“If the Prime Minister’s so-called deal goes through, it means we are in transition until the end of 2020 – but the risk of falling out on a No-Deal basis at the end of that is enormous, because it is implicit on him getting a free-trade agreement with Europe over that period.”

LibDem leader Jo Swinson said she hoped Labour would be able to “support” her party and the SNP’s bid for a December 9 election.

The Herald:

She told the BBC’s Andrew Marr programme that the Bill, due to be placed tomorrow, takes away the threat of No Deal via a Brexit extension until at least January 31, 2020.

“This removes that threat, so they should be able to support this proposal,” said Swinson.

She added: “This Bill is very straightforward. It would set the date for the next election on December 9. The advantage of the Bill is it would enshrine the date into law.”

The draft law, currently scheduled for Tuesday’s sitting, would require a simple majority of 320 MPs to support it in order to dissolve Parliament – 114 fewer than under the FTPA “super majority” rules.

With the SNP and Lib Dems supporting the initiative, the Bill is likely to pass even without Labour backing.

Downing Street indicated it could be willing to support the pro-Remain parties’ proposals in a possible compromise offer.

A Number 10 source said if the Government’s request for an election was lost, “we will look at all options to get Brexit done including ideas similar to that proposed by other opposition parties”.

The UK Government has requested a Brexit extension from the EU until January 31, but is still waiting to hear if it will be granted. If not, the UK will leave the EU without a deal 11pm this Thursday.

If passed on Tuesday, the SNP-Lib Dem Bill is likely to achieve Royal Assent by Thursday and Parliament would be dissolved by the end of the week for the first December poll in almost a century.