Nicola Sturgeon will insist that the UK is “not remotely prepared” to leave the European Union in less than two months time.
With 53 days left until the UK is due to formally leave the EU, the Scottish First Minister will use a speech in the US to call again for a second Brexit referendum.
Ms Sturgeon will also argue that the “chaos, confusion and uncertainty of Brexit” had made it “clearer than ever” that Scotland’s interests were “not properly served” by remaining part of the UK – accusing ministers in London of treating the country as “an afterthought”.
The First Minister and SNP leader is due to speak at Georgetown University in Washington DC as part of a tour of the US and Canada.
She will address an audience at Georgetown’s Institute for Women, Peace and Security, with the event taking place at the start of Women World Leaders Week.
Ms Sturgeon will use her speech to warn that without free movement of people – something Theresa May has repeatedly ruled out retaining when the UK leaves the EU – there is a “very real risk” Scotland’s working population will go into decline, with this bringing with it “severe economic and social consequences”.
She will say: “The UK is not remotely prepared to leave the EU in 53 days time. That’s been obvious for a while now.
“The UK Government should finally recognise that, and it should ask the EU to agree to put back the planned date for Brexit.”
Such a request would have to be backed up by an “achievable plan” – with Ms Sturgeon suggesting the UK Government could think again on plans to leave the single market and customs union.
But she will add that a “better option is to hold a further referendum on EU membership”.
Ms Sturgeon will say this should happen because there is no consensus within Parliament on what form Brexit should take, “and therefore the Scottish Government’s view is that this issue should be put back to the people”.
The First Minister will add: “That fundamental point – that no Scottish parliament, of any political composition, would approach Brexit in the way that the UK Government has – helps to explain why Brexit is also relevant to the debate on Scottish independence.
“In the independence referendum in 2014, voters in Scotland were repeatedly told that if we became independent, we would have to leave the European Union. Voting to stay in the UK was portrayed as the way to protect our EU membership.
“That in itself raises the question of whether decisions about Scotland should continue to be taken at Westminster – or whether it would be better if they were taken in Scotland.
“And now the ongoing chaos at Westminster and the way Scotland’s interests have been consistently ignored, makes that question even more relevant.
“So I have said I will outline my thoughts on the timing of a possible independence referendum in the next few weeks – once the terms of Brexit are clearer.
“But, amid the chaos, confusion and uncertainty of Brexit, one thing is clearer than ever.
“Namely, that Scotland’s vital national interests are not properly served by relying on the Westminster system which treats Scotland as an afterthought, and that those interests can only properly be served by being an independent country.”
A UK Government spokeswoman said: “Nicola Sturgeon needs to stop using Brexit as an excuse to pursue her unwanted independence agenda.
“Rather than constantly seeking division and constitutional upheaval, she needs to work with the UK Government to avoid a damaging no-deal. That is what people and business in Scotland expect.”