THERESA May has conceded the UK could break up as she gave what is expected to be her last speech in Scotland last night.

Speaking in Stirling ahead of a Tory leadership hustings in Perth this evening, she issued a warning to the two candidates that the Union could not be “taken for granted” and those who cared for it should “act wisely”.

READ MORE: Here are 10 of the most cringeworthy lines from May’s Scottish speech

May also suggested the SNP could not be trusted to act in “good faith”.

It came as First Minister Nicola Sturgeon accused the Tory PM of “high-handed arrogance”.

In her speech, May said the referendum in 2014 and the following year’s General Election, in which the SNP won 56 out of the 59 seats at Westminster, “sent shock waves throughout the UK”.

She also insisted her successor must deliver a Brexit for the whole of the UK as she launched an attack on the First Minister saying her claim that Brexit was being used as a “power grab” on Holyrood “was absurd”.

She said: “The only threat to devolution comes from those parties who want to end it by breaking up the United Kingdom.

“It was ironic that the UK Government’s sincere efforts to ensure that Brexit had no unintended consequences for the UK’s internal market was dismissed as a ‘power-grab’ by the SNP.

“On one level the allegation is simply absurd. On another, it highlights a challenge which faces the UK Government as it seeks to act in the best interests of the whole UK.

“Whereas the UK Government is invested in the success of devolution, it would suit the political aspirations of the present Scottish Government for devolution to fail, or to be seen to fail.

“The criticisms of the present First Minister about how our two governments interact need to be viewed in that context.”

READ MORE: Theresa May's full speech in Scotland on the Union

She added: “Over the last three years I have learned that while other parties can be relied on to work with the UK Government in good faith to make devolution a success, an SNP Scottish Government will only ever seek to further the agenda of separation.”

Sturgeon said May’s time in office had given lie to the myth of an “equal partnership” and boosted independence.

She said: “The way in which Theresa May has treated Scotland over the past three years is leading to an increase in support for independence.

“She’s conducted herself as prime minister in a high-handed and arrogant way that is completely dismissive of Scotland.

“She’s behaved as if the views of the majority on Brexit simply don’t matter, she’s shown zero respect for the Scottish Parliament and has done more than most to give lie to this notion that the UK is a partnership of equals.

“As people have experienced that over the past three years, many people, including some who voted no in 2014, have reconsidered that view and it’s why we see support for independence rising.”

READ MORE: Shona Craven: Was this May’s Plan A for avoiding a decoupling?

May gave further details of a review into how devolution is working and stressed it will not include devolved areas that are the responsibility of the Scottish Government.

The PM said: “We need to work more cleverly, more creatively and more coherently as a UK government fully committed to a modern, 21st-century Union in the context of a stable and permanent devolution settlement to strengthen the glue that holds our union together.

“There have been several reviews into how devolution works. But we have never thought deeply about how we make the Union work – how we ensure that as we fully respect devolution, we do not forget the UK Government’s fundamental duty to be a government for the whole United Kingdom of Great Britain and Northern Ireland.”