Theresa May has pledged to keep Scotland in the United Kingdom if she becomes Prime Minister after Nicola Sturgeon said EU nationals would be allowed to vote in a second independence referendum.

The Home Secretary and Tory leadership frontrunner promised that defending the Union would be a “major priority” for her if she wins the contest and that Scotland would be a “strong and integral part” of the UK.

In a direct appeal to blue collar voters, she said she would try to emulate Ruth Davidson’s success in Scotland by putting the Conservatives “at the service of ordinary, working people.” She concluded that she wants “a country that works for everyone, regardless of their background.”

But Ms Sturgeon attacked Mrs May’s refusal to guarantee that EU nationals already in the UK can stay here and pledged that those in Scotland would still be able to vote in a second independence referendum, as they could in the 2014 ballot.

This would be expected to drive up the vote for Scottish separation as the First Minister has pledged an independent Scotland would join the EU, although it is not clear on what terms and the timescale for this to occur.

The SNP leader has warned she will stage a second independence referendum unless some way can be found of keeping Scotland in the EU while the rest of the UK leaves - a prospect that experts, the Spanish government and the Foreign Office have rejected.