NICOLA Sturgeon has called a second independence referendum after insisting she “bust a gut” trying to get a bespoke Scottish Brexit only to be met with Westminster intransigence.

Barely 30 months after voters backed the Union 55-45 in a “once in a generation” choice, the First Minister announced there would be another poll between autumn 2018 and spring 2019.

The timetable, after Brexit negotiations are due to finish, would allow people to make an “informed choice” between independence and carrying on in the UK, she said.

READ MORE: Four in 10 Britons think Brexit has made independence more likely

Blaming Theresa May’s government for acting in bad faith over Brexit, Ms Sturgeon said she would seek authority from Holyrood next week for a transfer of referendum powers.

In a press conference at Bute House, her official residence in Edinburgh, the First Minister said her December proposal to keep Scotland in the EU single market had been repeatedly ignored by the Prime Minister, and she now had to act to protect the country’s interests.

“Our efforts at compromise have been met with a brick wall of intransigence,” she said.

“There has been talk of special deals for the car industry and others, but a point blank refusal to discuss in any meaningful way a differential approach for Scotland.”

She said her door was still open if the UK government changed its stance, but added: “I cannot pretend to the Scottish people that a compromise agreement looks remotely likely, given the hardline response from the Prime Minister so far.”

With her premiership now on the line, Ms Sturgeon said she expected to win the referendum, despite recent polls suggesting a wafer-thin majority for staying in the UK.

She later told The Herald: “We have bust a gut to get an agreement with the UK Government. If they had been less intransigent we would not have been standing where we are today.

“It has been impossible to get an agreement and they have continued to string us along. It has been really frustrating.”

Asked about another independence campaign distracting her from governing, she said: “It’s a false distinction to make between a campaign and what people call ‘the day job’.

“The NHS and education will remain top priorities and an integral part of what we are doing.”

The request for a Section 30 Order to transfer referendum powers to Holyrood is expected to be passed easily next week, as SNP and Green MSPs make up a pro-independence majority.

It will then be for the UK government to decide whether to agree.

Although Downing Street has long insisted people do not want a second referendum and the No vote of 2014 should be respected, it will be difficult to resist the will of the Scottish Parliament, not least because it could boost support for independence.

READ MORE: Four in 10 Britons think Brexit has made independence more likely

However the UK Government could attach conditions to a transfer of power, potentially delaying a referendum until after Brexit in 2019.

Stonewalling on whether she would permit a referendum, Mrs May said the announcement was “deeply regrettable” and had set Scotland on course for “more uncertainty and division.”

She said: “Instead of playing politics with the future of our country, the Scottish Government should focus on delivering good government and public services for the people of Scotland. Politics is not a game."

After weekend briefings that she could trigger the Article 50 withdrawal process today, the Prime Minister last night delayed starting Brexit talks until March 27.

Number 10 denied the move was related to Ms Sturgeon’s announcement.

Scottish Secretary David Mundell added: “Of course there could be another referendum, that would require an Edinburgh Agreement process but we don’t believe there should be.

“We are going to continue to make that case because we believe that is what the people of Scotland want. They don’t want another divisive independence referendum.”

Opposition leaders at Holyrood also criticised Mr Sturgeon, accusing her of an “utterly irresponsible” decision to put the SNP’s top priority ahead of the needs of voters.

Scottish Conservative leader Ruth Davidson said the SNP leader had "given up acting as First Minister for all of Scotland".

At Bute House, Ms Sturgeon said she had been driven to call another referendum by the prospect of a Tory-led hard Brexit which did not reflect the 62-38 Remain vote in Scotland and which would not only damage Scotland’s economy but fundamentally change society.

She said: “It has implications for jobs, opportunities, public spending, and living standards - and for our ability to protect and advance our vital day to day priorities in education, health and business. It has implications for our society - how open, welcoming, diverse and fair we will be in future? And it has implications for our democracy - to what extent will we be able to determine our own direction of travel, rather than having it decided for us?

“In short, it is not just our relationship with Europe that is at stake. What is at stake is the kind of country we will become.”

Doing nothing during two years of Brexit negotiations was not an option, she said, and so she would “make sure that Scotland will have a choice at the end of this process”.

She said: “If Scotland is to have a real choice - when the terms of Brexit are known, but before it is too late to choose our own course - then that choice should be offered between the autumn of next year, 2018, and the spring of 2019.”

Insisting she had a mandate to hold a referendum based on last year’s SNP manifesto, she said: “I am ensuring that Scotland's future will be decided not just by me, the Scottish Government or the SNP. It will be decided by the people of Scotland. It will be Scotland's choice. And I trust the people to make that choice.”

Ms Sturgeon said she would be “frank about the challenges” and Scotland would make an “informed choice”.

However when asked what currency an independent Scotland would use, she replied “all in good time” and failed to say if independence would mean re-joining the EU.

Labour MP Pat McFadden MP, of the Open Britain group, said the UK Government’s “headlong rush to hard Brexit” had boosted the Nationalists.

He said: “Ministers now need to deal with the very real prospect of the breakup of the Union, that many of us thought we had secured the future of in 2014.”

The European Commission indicated an independent Scotland would have to apply to join the EU, rather than continuing inside it.

A spokesman said the "Barroso doctrine" would apply, meaning the legal view that if one part of an EU country became an independent state it would have to apply for EU membership.

Nato secretary-general Jens Stoltenberg also said an independent Scotland would leave the military alliance if it left the UK, and would "not automatically" be allowed to rejoin, as that would depend on the agreement of all 28 Nato allies.

Spain, which is wary of encouraging the secessionist movement in Catalonia, could veto both EU and Nato membership.

Former First Minister Alex Salmond said he had "absolutely no doubt there will be a resounding vote in favour of independence".

READ MORE: Four in 10 Britons think Brexit has made independence more likely

Plaid Cymru leader Leanne Wood said a vote for independence vote could signal “the end of the UK as a state”, adding: “In that situation, Wales would need to decide its own future.”

Paul Johnson, director of the Institute for Fiscal Studies, said that with public spending £1,000 higher per person in Scotland than in the rest of the UK despite similar tax revenues, independence could mean large tax hikes or deep spending cuts.

The Scotland in Union group will today launch a campaign aimed at No voters who feel angry their vote in 2014 has been ignored.

Chief executive and former Labour MSP Graeme Pearson will argue a second referendum “is not inevitable" if enough people speak out.