THERESA May has accused the SNP leadership of being "obsessive" Nationalists, who have used the Brexit vote to try to engineer a second Scottish independence referendum.

She also accused Nicola Sturgeon and her colleagues of being in a “muddle” over their approach to the European Union.

Speaking at the Conservative Spring Forum in Cardiff, the Prime Minister unveiled her vision for the country, a Plan for Britain, which put strengthening and sustaining the Union “at its heart”.

READ MORE: Former Prime Minister Gordon Brown proposes 'Scottish patriotic way' of federal UK to avoid 'bitter division'

Saying how the Tories now represented the "new centre ground" of British politics, she told delegates: “Our party believes heart and soul in our United Kingdom of Great Britain and Northern Ireland. The precious bond between four nations: England, Scotland, Wales and Northern Ireland. But that Union is more than just a constitutional artefact, it is a Union between all of our citizens, whoever we are and wherever we’re from.”

Mrs May said her vision of a fairer and united Britain meant putting the national interest above any other consideration. It meant ensuring the UK Government acted in the interests of the whole country, creating jobs and supporting cities, towns and communities right across the UK.

The PM insisted that, as the party of the new centre ground of politics, the Conservatives rejected the “extremes of Labour’s socialist left, UKIP’s libertarian right, and the divisive and obsessive nationalisms of Plaid Cymru and the SNP”.

She claimed Nationalist tunnel-vision had been on display this week.

“The SNP argue that we should break up the UK because we are leaving the EU. But three years ago they campaigned for a result that would have taken Scotland out of the EU altogether.

“They are happy to see power rest in Brussels but if those powers come back to London they want them given to Edinburgh, so that they can try to give them back to Brussels.”

She went on: “Now, they apparently say that an independent Scotland would no longer seek to become a member of the EU after a vote for separation. It is muddle on muddle.

“The fact that more Scottish voters backed Scotland staying in the UK in 2014 than supported the UK staying in the EU in 2016 and that almost half a million independence supporters actually backed Brexit last year seems to count for nothing,” noted the PM.

She claimed it was now clear that using Brexit as the pretext to engineer a second independence referendum had been the SNP’s sole objective since the referendum last June.

Mrs May argued that with the Brexit negotiations coming up the country had to focus all its energies on trying to get the best deal for the whole of the UK.

READ MORE: Former Prime Minister Gordon Brown proposes 'Scottish patriotic way' of federal UK to avoid 'bitter division'

“We can only get that deal if we are united, as one United Kingdom, all pulling together to get the best outcome. That is what we have always done when faced with challenges. We have pulled together as one and succeeded together.”

The PM added: “We are four nations but at heart we are one people. As the Prime Minister of this United Kingdom, I will always ensure the voices and interests of England, Scotland, Wales and Northern Ireland are represented as we negotiate to leave the EU.

“And I will always fight to strengthen and sustain this precious, precious Union.”