A matter of hours before the Scottish Parliament is due to back Nicola Sturgeon’s demand for a second independence vote, the Prime Minister clashed with Mr Robertson in Westminster.
The SNP have insisted a second ballot on independence must come after the terms of Mrs May’s final Brexit deal are known but before the UK’s exit from the EU is complete.
But the Prime Minister has steadfastly refused to meet that demand, telling Ms Sturgeon “now is not the time” for a fresh Scottish referendum on breaking up the UK.
Mr Robertson attacked Mrs May over her unwillingness to agree to the SNP’s timetable, which would see a second independence referendum held at the same time as the UK’s Brexit deal was being ratified across Europe.
During Prime Minister’s Questions, Mr Robertson – the SNP’s deputy leader – asked: “The Prime Minister says that she wants Article 50 negotiations to lead to a deal and she wants people to know the outcome of that deal before it is approved.
“Will the Prime Minister confirm that in the period for an agreement the House of Commons will have a choice, the House of Lords will have a choice, the European parliament will have a choice, 27 member states of the EU will have a choice.
“If it’s right for all of them to have a choice about Scotland’s future, why should the people of Scotland not have a choice about their own future?”
But the Prime Minister reminded Mr Robertson how it is still less than three years since the Scottish public voted against independence.
She replied: “This isn’t a question about whether the people of Scotland should have a choice or not. The people of Scotland exercised their right to self-determination and voted in 2014 to remain a part of the UK.
“The people of the UK last year voted to leave the EU. We are respecting both of those votes. He is respecting neither of them.”
Theresa May clashed with Angus Robertson in the House of Commons
Mr Robertson had used his previous question to condemn the Prime Minister for failing to agree to Ms Sturgeon’s demand for a different Brexit deal for Scotland to the rest of the UK.
He said: “Last year, the Prime Minister promised that she would secure a UK-wide agreement between the governments of Scotland, Wales, Northern Ireland and her government before triggering Article 50 on Brexit.
“Since then she has delayed, she has blocked, she has been intransigence and she has lectured and surprise, surprise, she has no agreement. There is no agreement.
“Will these be her negotiating tactics with the EU?”
Mrs May told Mr Robertson “every effort has been put in at various levels of ministerial and official level to work with all the devolved administrations” ahead of upcoming EU exit negotiations.
The Prime Minister added: “What we want to ensure is that we get the best possible deal when we leave the EU for all the people of the UK, including the people of Scotland, because at heart we are one people.”
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The SNP are likely to win a vote in the Scottish Parliament later on whether MSPs back their demand for a second independence referendum.
Despite not holding a majority in the Holyrood chamber, Ms Sturgeon has secured the support of pro-independence Scottish Green MSPs.