A vote for Labour would see Jeremy Corbyn “dancing to the SNP’s tune” to break up Britain in 2020, Boris Johnson has insisted ahead of his first campaign visit to Scotland today.

The Prime Minister will try to get the Conservative campaign back on track after the resignation of Alun Cairns, the Welsh Secretary - in wake of the rape trial “sabotage” row - cast a shadow over the Tories’ official launch with a speech by Mr Johnson in Downing St and a rally in the West Midlands.

Stephen Crabb, the former Welsh Secretary, admitted his successor’s resignation - the first by a serving Cabinet minister during a General Election since at least 1900 - was "very damaging" to the Conservatives’ campaign in Wales.

The PM, who is expected to make a whistle-stop call to a Tory-held seat in the north-east this afternoon, declared: “This is a crucial election for Scotland. A vote for the Scottish Conservatives is a vote to stop a second independence referendum and to get Brexit done so we can spend 2020 taking back control of our fishing waters, getting a fairer deal for our farmers, and investing in public services to give people better healthcare and better education.

READ MORE: Neil Mackay: A new vision for Scottish independence: how we can change our broken politics 

“The other choice is a vote for Jeremy Corbyn, who would spend next year dancing to the SNP’s tune, wasting the year with two divisive referendums; one on the EU and one to give up on our Union.”

He added: “Only a vote for the Conservatives will stop the SNP’s plans to break up the UK, the most fantastic and successful political union in the world. I will never give up on our incredible Union.”

Last night, Nicola Sturgeon hit back, saying the only thing Mr Johnson should be coming to Scotland to do was to “apologise for the chaos he and his party have subjected us to for years. He is a prime architect of the Brexit vote and the utter shambles it has now led to”.

The First Minister added: “A vote for the SNP is a vote to escape Brexit and to put Scotland's future in Scotland's hands; not Boris Johnson's.”

It is thought the PM will this lunch-time visit a local distillery, raising speculation he will confirm a Government review of spirit duty should the Conservatives be returned to power.

On Tuesday night, Mr Johnson spoke to Donald Trump when he urged the American President to lift tariffs on goods, including scotch whisky, following concerns the newly imposed US tax could wipe £1 billion off single malt sales during the next year.

Also today, Sajid Javid, on a campaign visit to north-west England, will attack Mr Corbyn’s “fantasy economics,” saying they would wreck Britain’s recovery and he will warn having two referendums on EU membership and Scottish independence next year would leave “business-facing even more uncertainty”.

The Chancellor will liken Mr Corbyn and his Shadow Chancellor John McDonnell to the “anti-vaxxers of economic policy,” saying: “Not only did they reject the treatment needed to heal our economy and get the deficit down by four-fifths, they now want to take every step imaginable to make the country sick and unhealthy again...

"The best thing for our economy is to get Brexit done,” Mr Javid will declare.

Last night, Mr Johnson launched his party’s election campaign with a tub-thumping rally in the West Midlands when he echoed his message from earlier in the day.

Standing behind a lectern in Downing St, the PM said there was a straightforward choice on December 12.

“Come with us, a government that believes in high wages and is raising the living wage to £10.50, the biggest ever increase or go with a left-wing Labour Party that believes in high taxes for everyone and voted against £7,800 of tax cuts on working people.”

READ MORE: Scottish Labour leader: There will be no deals with the SNP at Westminster

After highlighting differences between the Tories and Labour on education, immigration and foreign policy, the PM declared: “Come with us and get Brexit done and take this country forward or, this is the alternative next year, spend the whole of 2020 getting a horror show of more dither and delay.

“Imagine waking up on Friday December 13 and finding Corbyn at the head of his technicolour rainbow coalition.

“They would spend the whole of 2020 having two referendums; one on Scotland - because he has done a deal with the Scots Nationalists to assist the break-up of the Union to sustain him in power - and another referendum on Brexit, which is supposed to happen in nine months’ time after he has renegotiated, supposedly, this deal.”

He added: “There is only one way to avoid that nightmare and that is to vote for a compassionate, One Nation Conservative government.”

Just minutes before Mr Johnson’s appearance in Downing St Mr Cairns resigned his Cabinet post.

In a letter to the PM, the 49-year-old, who has been MP for the Vale of Glamorgan since 2010, said he was “confident” he would be cleared of any wrongdoing by a Whitehall inquiry.

Mr Cairns claimed he had only become aware of Ross England's role in the trial's collapse when the story broke last week. But it emerged he was emailed about it in August 2018, four months before Mr England was chosen as the Tories’ Vale of Glamorgan candidate for the Welsh Assembly.

In the trial of his friend James Hackett, Mr England said he had had a sexual relationship with the complainant - which she denied - despite any evidence about the victim’s sexual history having been ruled inadmissible.

The judge said Mr England’s action was a deliberate attempt to “sabotage” the trial. Hackett was later convicted of rape at a retrial.

Last week, Mr England was suspended as a Tory candidate after details of the court case emerged. The party said a full investigation would now be undertaken.

Mr Cairns’ rivals in the election insisted he should now stand down as an election candidate.

In other developments:

*James Cleverley, the Tory Chairman, defended the doctoring of a video of Labour's Keir Starmer, describing it as "light-hearted satire";

*a row broke out in Whitehall between Mr Javid and Sir Mark Sedwill after the Cabinet Secretary refused to sanction plans for the Treasury to publish a cost analysis of Labour’s election policies and

*David Mundell, the former Scottish Secretary and the Conservatives’ candidate for the borders seat of Dumfriesshire, claimed the "only job" of SNP MPs would be to secure another independence vote.