NICOLA Sturgeon will this week take the constitutional fight to Boris Johnson over a second independence referendum with the possibility that a legal challenge could be mounted as the SNP vows to do “absolutely everything” to secure a 2020 vote on Scotland’s future.

Discussions by the Nationalists’ high command were taking place last night over the pros and cons of the First Minister visiting Westminster for a Downing St showdown with Boris Johnson but party sources pointed to the emphasis being on this week’s formal request by the Scottish Government for Holyrood and not Westminster to have the power to hold another independence poll.

On the back of the SNP’s landslide victory, gaining 48 of Scotland’s 59 seats, Ian Blackford, the party’s Westminster leader, will make a statement today as he welcomes his strengthened parliamentary contingent to the House of Commons.

A senior SNP source told The Herald: “We are not going to give up on having a referendum in 2020 whatever Boris says but if he digs in, it might well be the case we end up at the Holyrood election in 2021.”

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Asked if a possible court challenge could be on the cards, he replied: “We will spell out this week what we plan to do; we have to show leadership on this. We have game-planned everything. We will do absolutely everything we can to make sure that referendum takes place next year.”

Earlier, Ms Sturgeon condemned the “dictatorial attitude” of the Prime Minister, saying the “perversion and subversion of democracy…will not hold” and insisted: “Scotland cannot be imprisoned within the United Kingdom against its will.”

She claimed Mr Johnson was “utterly wrong” if he thought just saying no would be an end to the matter and warned continuing Tory intransigence would simply boost support for independence.

“You cannot hold Scotland in the Union against its will; you cannot sort of just lock us in a cupboard and turn the key and hope that everything goes away,” the FM told BBC TV’s Andrew Marr Show.

But Michael Gove, the Cabinet Office Minister, made clear even if the SNP won a Holyrood majority in 2021, the new Conservative Government would not facilitate indyref2.

And Jackson Carlaw, the acting Scottish Tory leader, condemned Ms Sturgeon’s language, claiming she was "losing the plot" and had descended into becoming a "Nationalist rabble-rouser".

On Friday evening, Mr Johnson told her in a telephone call that he had no intention of allowing a second poll; last week he told The Herald the 2014 vote was “for good”.

Speaking on Sky News’s Sophy Ridge on Sunday programme, Mr Gove emphasised that the UK Government would "absolutely" not hold another public vote on Scottish independence during the course of the 2019-2024 Parliament regardless of how Scotland voted in the 2021 Holyrood election.

Asked if the Tory Government’s refusal to facilitate indyref2 would last for the whole Parliament, the Scot replied: “We were told in 2014 that that would be a choice for a generation; we are not going to have an independence referendum in Scotland.”

He added: “In this General Election we have just seen what happens when politicians try to overturn a referendum result and in the same way we should respect the referendum result of 2014.”

After the third General Election in four years, MPs will gather at Westminster on Tuesday to be sworn in.

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The Government will set out its legislative programme in a new Queen’s Speech on Thursday, shorn of its usual full pomp and ceremony. The programme is expected to include a commitment to enshrine in law Mr Johnson’s "number one priority" to increase NHS spending by £34 billion by 2023/24; which would result in a consequential windfall for the Scottish Government of around £3bn.

The First Reading of the Withdrawal Bill is due this week too, possibly on Friday, to meet the pledge to begin the Brexit process before Christmas. With a majority of 80 the Tory leader should have no problem getting it through.

He is expected to address his newly elected colleagues at Westminster at a private meeting in the Commons.

A No 10 source said: "This election and the new generation of MPs who have resulted from Labour towns turning blue will help change our politics for the better.

"The PM has been very clear we have a responsibility to deliver a better future for our country and that we must repay the public's trust by getting Brexit done.

"That's why the first piece of legislation new MPs will vote on will be the Withdrawal Agreement Bill," he added.

The PM is also expected to make a few changes to his top team given Nicky Morgan, the Culture Secretary, stood down at the election, Alun Cairns, the Welsh Secretary, resigned his role, and Zac Goldsmith, the Environment Minister, lost his London seat.

The bill’s full passage will take place in January ahead of the 31st deadline with a major Cabinet reshuffle, when up to a third of its membership could be changed, pencilled in for February.

Sources suggested Mr Johnson is preparing for a “revolutionary” Government with a strong emphasis on the NHS and a whole Government shift to improve the lives of working-class people in northern England; voters who secured him his election victory.

The PM is expected to use his Christmas break to reconfigure Whitehall, not only sacking ministers and bringing in a new team but also scrapping and merging departments as well as replacing civil servants with outside experts to reshape the economy.

The changes are expected to include:

*abolishing the Brexit Department;

*merging the Trade and Business Departments to focus on the EU trade deal and boosting the economy in northern England;

*merging the Foreign Office and the International Aid Department and

*remove energy and climate change from the Business Department.

Mr Johnson this week is expected to discuss with Alister Jack the recommendations of the Dunlop Review into how devolution works.

The report into the so-called “Union capability” was commissioned by Theresa May just weeks before she left Downing St to see how the way Government operated could “strengthen and sustain” the Union.

It is thought neither the PM nor his Scottish Secretary has yet seen the report, which, it is claimed, recommends the establishment of a Department for the Union; something first mooted but rejected during the early years of the Blair Government. The discrete issues of Northern Ireland were seen as a barrier to its creation.

Some Tory MPs have previously called for a Department for the Union with the PM’s deputy, the First Secretary of State, appointed to head it to underscore how strengthening and protecting the UK was at the heart of a One Nation Conservative administration.

One senior Government insider told The Herald that the thinking inside Whitehall was not for a new department but, rather, for the newly-created Downing St Union Unit to be “beefed up” with a strong input from the Cabinet Office headed by Mr Gove.

“The ink is barely dry on the report but we are going to have to do big things in Scotland. Our One Nation ambition is for the whole of the UK but particularly Scotland,” said the senior source.