May will also unveil plans for a review into the role of Whitehall departments in the devolved nations, in a move expected to lead to increased direct spending by the UK government in Scotland, Wales and Northern Ireland.
She will travel to Scotland on the eve of a widely anticipated Conservative leadership hustings between Boris Johnson and Jeremy Hunt in Perth on Friday evening, which is likely to focus heavily on Holyrood’s powers.
Recent opinion polls show increased support for independence, particularly if Johnson becomes prime minister and presses ahead with a no-deal Brexit. A Panelbase poll for the Sunday Times last weekend put the yes vote at 49%, excluding don’t knows, with 51% favouring a referendum if the UK leaves the EU.
Nicola Sturgeon, Scotland’s first minister, tweeted that May’s visitwas “a desperate act by a prime minister who has shown zero respect for the Scottish parliament during her time in office”.
She added: “It’s for the Scottish people – not a Tory PM – to consider and decide what future we want for our parliament and country.”
Sturgeon has said she wants a fresh independence referendum later next year, and has tabled legislation to enable referendums to take place in Scotland if the UK government hands Holyrood the powers to stage one.
Both Johnson and Hunt have ruled out giving her those powers but senior Scottish Tories fear the Brexit crisis and Johnson’s expected victory in the leadership election will substantially boost support for an early independence referendum.
Whitehall sources say May’s review, which will be headed by the former Scotland Office minister Lord Dunlop, will focus on giving UK departments an enhanced role in devolved countries in an effort to strengthen the union and share its resources.
One source said the prime minister wanted Whitehall departments to stop treating devolved nations as areas they were no longer concerned with. The Scotland Office and Wales Office are likely to be enlarged rather than merged into a new department.
“We’re trying to get a real shift in mindset in Whitehall,” he said. “The emphasis needs to be not so much on the mechanics of devolution. The emphasis needs to be much more on sustaining the union.”
He pointed to UK government funding for a new 1,000-seater concert hall in central Edinburgh designed by Sir David Chipperfield and a rescue package to save Perth city hall from demolition. Both came through city deals jointly funded by the UK and Scottish governments, but both projects would normally be regarded as devolved policy areas.
It is thought Johnson and Hunt support May’s proposed review but have said they will not be bound to accept Dunlop’s recommendations.
Recent opinion polls have also shown that Scottish voters trust the Scottish government far more than the UK government – a trend that has grown with successive Tory governments in power in London.
The Scottish National party has a clear and substantial lead over the Conservatives and Labour in polling on both Holyrood and Westminster elections, with voters putting much greater emphasis on Europe and the future of the UK since the 2016 EU referendum.
Ian Blackford, the SNP’s Westminster leader, believes Johnson may call a snap general election before the end of October in attempt to win a mandate for a no-deal Brexit. There is also speculation Johnson would call an election later in the year if the Commons votes down his Brexit plans.
Under either scenario, Scottish Tories have warned Johnson and Hunt they face losing many of the 13 seats they won in 2017.
Jeremy Corbyn, the Labour leader, has been told Labour has no hope of winning the 20 Scottish seats he needs to secure a Commons majority if he continues to back Brexit.
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