Nicola Sturgeon has claimed that independence will be Theresa May’s ultimate legacy as the Prime Minister makes her last official visit to Scotland.

The First Minister said the “high-handed, arrogant and dismissive” attitude of the Tories over Brexit had shattered any illusion that the Union was a partnership of equals.

She also said there was nothing Mrs May’s successor could do “to undo the damage to the Unionist cause which has been inflicted during her premiership”.

However the PM will use her farewell trip to Scotland today to stiffen the resolve of her successor to “protect the Union,” telling Boris Johnson and Jeremy Hunt on the eve of a Tory leadership hustings in Perth tomorrow that they must prioritise defending the integrity of the United Kingdom.

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She will say: “The job of Prime Minister of the United Kingdom of Great Britain and Northern Ireland brings with it privileges and responsibilities which you only really feel once the black door closes behind you.

“One of the first and greatest is the duty you owe to strengthen the Union. To govern on behalf of the whole United Kingdom. To respect the identities of every citizen of the UK; English and Scottish, Welsh and Northern Irish.

“And to ensure that we can go on facing the future together, overcoming obstacles together, and achieving more together than we ever could apart; a Union of nations and people.”

One Whitehall insider described her final speech in Scotland before her successor is named on July 23 as “inspirational,” saying it presented a “heartfelt intellectual case for maintaining the Union”.

The PM is also expected to announce a snap review of whether Whitehall is doing enough to strengthen the Union after 20 years of devolution.

It will be undertaken by the former Scotland Office minister Lord Dunlop, who recently observed Ms Sturgeon at work from the Holyrood gallery during First Minister’s Questions.

But Ms Sturgeon said Mrs May’s three years in Downing Street had only laid bare the differences between Scotland and the rest of the UK.

She said: “Scotland is heading inexorably towards independence - that will be Theresa May’s legacy. The Tories’ behaviour towards Scotland in the three years since the Brexit vote has been high-handed, arrogant and dismissive.

“They have demolished any notion of a respect agenda and have destroyed their own claims that the union is in any meaningful way a partnership of equals.

“People across Scotland can now see that more plainly than ever.”

Ms Sturgeon also criticised Mrs May’s repeated refusal to grant Holyrood the power to hold a second independence referendum to avoid leaving the EU.

The latest opinion poll put support for a Yes vote at 49 per cent, or 53 per cent if Mr Johnson, who has promised Brexit “do or die” by Hallowe’en, is PM.

The First Minister went on: “The Tories are clearly running scared of the rising tide of support for independence - and of support for holding an independence referendum, which is now the majority view across Scotland.

“Theresa May’s so-called review of devolution is too little, too late – it is reminiscent of John Major’s doomed ‘taking stock’ exercise in the 1990s, which only accelerated the pace towards the devolution referendum and the creation of Holyrood.

“This is Theresa May’s last visit to Scotland as Prime Minister – but there is nothing that her successor, whoever that is, can do to undo the damage to the Unionist cause which has been inflicted during her premiership.”

During PMQs yesterday, SNP Westminster leader Ian Blackford dismissed what he called Mrs May’s “review of devolution” as a farce, telling MPs: “The real legacy of this Prime Minister is shutting down Scotland and ignoring the will of the Scottish Parliament. The Tories have never supported devolution and it is clear that they never, never will.”

But Mrs May hit back, insisting there was “no review of devolution” per se, adding: “Only one party in this House wants to stop devolution in Scotland: the Scottish National Party.”

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Her spokesman later stressed: “Categorically, what this is not about is in any sense reviewing, questioning, changing the devolution settlement as it currently stands.”

Deputy Scottish Tory leader Jackson Carlaw added: “The reality is that Nicola Sturgeon is heading inexorably towards an even deeper state of denial and delusion.

“Despite trying every trick in the book, her attempts to whip up grievance and resentment over the last four years have failed.

“Whatever she claims, most people don’t want another independence referendum, they want Nicola Sturgeon to focus for once on improving our schools and public services.

“The Prime Minister’s plan to improve the way the UK operates is welcome and sensible. Nicola Sturgeon’s desperate headline grabbing will impress no-one.”