Nicola Sturgeon and Theresa May are locked in a fierce constitutional battle after the first minister demanded the right to hold a second independence referendum within two years.
The SNP leader will next week seek the approval of Holyrood to start negotiations with the UK Government on a deal to allow a legal ballot to be held.
She said a second vote would take place between autumn 2018 – just four years on from when Scots voted by 55% to 45% to stay part of the United Kingdom – and the spring of 2019.
The Press and Journal revealed last month that Downing Street was “war gaming” for a push for another referendum to be held in August next year, a month before the time period cited by Ms Sturgeon.
Prime Minister Theresa May accused the first minister of “playing politics with the future of our country” after the announcement.
Ms Sturgeon claimed, though, that her “compromise” proposals on Europe, which would allow Scotland to stay in the single market when the UK exits the EU, had been met with a “brick wall of intransigence” from UK ministers.
She said: “There should be little doubt about this – if Scotland can be ignored on an issue as important as our membership of the EU and the single market, then it is clear that our voice and our interests can be ignored at any time and on any issue.”
Leaving the EU would impact on jobs and the economy north of the border, as well as how “open, welcoming, diverse and fair” Scotland would be in the future, the first minister added.
She said: “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.”
A poll by BMG yesterday showed around four in 10 Scots support another vote on independence before Brexit happens, with voters split 52-48 in favour of staying in the Union.
Powers over referenda sit with Westminster, meaning any new vote needs the Houses of Parliament approval for a Section 30 order, which would transfer responsibility to Holyrood.
Ms Sturgeon claimed that a rejection, or an attempt to shift the timing away from her favoured period, would be equivalent to the UK Government “puncturing Scotland’s lifeboat having sunk the ship” with Brexit.
Downing Street officials were last night reluctant to engage in any speculation about what will happen when a request is made.
The prime minister’s official spokesman said No 10 was “waiting for the Scottish Parliament to reach a decision” on another vote.
Mrs May said: “The tunnel vision the SNP has shown today is deeply regrettable, it sets Scotland on a course for more uncertainty and division creating huge uncertainty.
“And this is at a time when the evidence is that the Scottish people, the majority of the Scottish people, don’t want a second independence referendum so instead of playing politics with the future of our country the Scottish Government should focus on delivering good government and services for the people of Scotland.
“Politics is not a game.”
It has also emerged that an SNP website to promote the pro-independence campaign was set up last month.
A Scottish Labour source: “No-one serious believes this was a snap decision from the Nationalists. They’ve been planning every day since 2014 on how to divide us again.”