THE FRONTRUNNER to become the next prime minister has accused Nicola Sturgeon of “leading a campaign of deception” as she ruled out granting permission for an independence referendum.

Liz Truss, who is favourite to succeed Boris Johnson as Tory leader, has hit out at the Scottish Government’s plans to press ahead with its independence campaign.

The Foreign Secretary has claimed the proposed Holyrood referendum legislation “isn't legal”.

The Supreme Court is yet to determine whether the bill is competent within the scope of devolved power.

The Scottish Government has asked the Supreme Court to give a view on whether Holyrood has the powers to hold a referendum on independence.

If no legal route emerges for Holyrood to hold its own referendum, Ms Sturgeon has insisted that the next UK general election will be a “de facto referendum” on independence.

Speaking to the Sunday Telegraph, Ms Truss said: "I will work to strengthen our whole Union.

“As prime minister, I will do what is necessary and right to defend our Union, just as I have already done on the Northern Ireland Protocol."

She added: "The SNP lost the 2014 referendum and Nicola Sturgeon is now leading a campaign of deception to steamroller the UK and break up the Union.

"But I am completely clear that there will be no second Scottish independence referendum on my watch.

"The Scottish Independence Referendum Bill isn't legal and it will be invalidated if passed by the Scottish Parliament. When Westminster devolved power to Scotland, it did not include the ability to hold valid referenda to break up the Union.

"Any Scotland independence referendum would need to be authorised by the Westminster Parliament. If I become prime minister, I would not grant that authority."

The First Minister has criticised Ms Truss and her rival Rishi Sunak over their views on the constitution – branding th leadership hopefuls “hypocrites”.

She said: “Liz Truss talking about the importance of referenda in settling constitutional issues, Rishi Sunak a few years ago saying that there should be a referendum after Brexit — well we are after Brexit. “They’re hypocrites — changing their position just to suit their narrow, party-political, democracy-denying agendas.”

SNP depute leader Keith Brown said: “It is crystal clear that the people of Scotland and Scottish democracy mean nothing to either of the contenders for next Tory prime minister.

“But people across Scotland will not stand for yet another Tory prime minister we didn’t vote for denying the cast-iron mandate to hold an independence referendum of a government and parliament we overwhelmingly voted for.

“With each day that passes, both Tory candidates are showing how out of touch they are with people across Scotland as they prioritise trying to outdo each other on Brexit, ducking their duties to support struggling households, and standing in the way of Scotland’s right to choose its future – Scotland deserves so much better.

“Scots voted for the chance to choose a better future in an independence referendum and – whoever becomes the next leader of the Tories – that future as a wealthier, fairer and more equal independent country is more vital than ever.”