Scotland's first minister, Nicola Sturgeon, said on 2 June that Prime Minister David Cameron could provoke another independence vote if he failed to secure Britain's continued EU membership, as Edinburgh sees its future in Europe.
In a speech setting out the stark differences between the Scottish and the British governments' positions on the EU, Sturgeon said a British exit from the bloc would spark a Scottish backlash against London.
"I previously stated my view that if Scotland were to be taken out of Europe despite voting as a nation to have remained, it would provoke a strong backlash amongst many ordinary voters in Scotland," Sturgeon said.
Cameron has promised to renegotiate Britain's ties with the EU before a membership referendum by the end of 2017 to meet criticism from some, particularly in Cameron's Conservative party, that the bloc's institutions have become overbearing.
Sturgeon said Scots, who polls show to be far more in favour of remaining in the EU than the English, would not accept being outside the bloc if a majority of British people vote to leave in a referendum.
"I believe that the groundswell of anger among many ordinary people in Scotland in these circumstances could produce a clamour for another independence referendum that may well be unstoppable," the Scottish National Party leader said.
Sturgeon said she believed Britain's constituent nations of Scotland, England, Northern Ireland and Wales should be required individually to support a British withdrawal for it to go ahead, a so-called 'double majority' that is a feature of federalism in Canada.
"If the UK is, as we are told, a family of nations where each one has an equality of status then nobody should be able to dictate to anybody else. And, you know, if it was the case that it was just a vote right across the UK then that means that just by sheer force of numbers, that how England votes decides it and how Scotland, Wales and Northern Ireland votes doesn't matter in that sense so I think it is much fairer and more democratic in that multinational state if we agree as a principle that we will only come out of the EU if each member of that multinational state chooses to do so," Sturgeon said.
Most business leaders in Britain strongly oppose the prospect of the country leaving the EU, the biggest market for British goods, while international partners from the United States to Germany and Ireland have made it clear they oppose a British EU exit and think it would isolate Britain.