Boris Johnson today sets out his desire to establish an Australian points-based immigration system and points to a willingness to address specific Scottish needs on migration.

As the Tory leadership campaign becomes more fractious with each candidate attacking the other over their Brexit plans, Jeremy Hunt received the support of Ruth Davidson and a majority of Conservative MSPs.

In a tweet, the Scottish Tory leader – who backed Sajid Javid and Michael Gove in previous rounds – said: “Any Conservative leadership candidate must put the Union first. Jeremy has done so and will get my vote.”

In response, the Foreign Secretary, who has hinted he might put Ms Davidson in his Brexit negotiating team, tweeted: “Thanks @RuthDavidsonMSP. Protecting our Union is vital. It’s an absolute honour to have you on board.”

Later, during a digital hustings, Mr Hunt said: "I don't want to go so far as to say I'm the living embodiment of the Union but I do have Welsh blood and I do have Irish blood and I did two very happy years of my childhood in Scotland.

"I just want to be very straight forward about this: I will never allow our Union to break up; never, never, never."

Meanwhile, Mr Johnson insisted: "We need to come out of the European Union on October 31 and get it done," suggesting it was “a million to one against” Britain leaving without a deal but the country had to prepare for it.

Emphasising his Leave credentials, he added: "We need somebody who believes in that project, who has campaigned on that project for many years and who knows how to get a good deal out of Brussels."

As the two candidates prepare for four more hustings in the next 72 hours, Mr Johnson set out his plans on immigration.

He said: “We will restore democratic control of immigration policy after we leave the EU. We must be much more open to high-skilled immigration such as scientists but we must also assure the public that, as we leave the EU, we have control over the number of unskilled immigrants coming into the country. We must be tougher on those who abuse our hospitality. Other countries such as Australia have great systems and we should learn from them.”

As part of his plan, the former Foreign Secretary wants the Government’s advisor, the Migration Advisory Committee[MAC], to engage with the Scottish Government to assess the impact of proposals on Scotland to ensure “regional concerns can be addressed on a rolling basis”.

Yet much of what Mr Johnson appears to be proposing, the UK Government is already set on doing.

It is introducing statutory changes, which will end the free movement of people and apply the same immigration system for all nationalities.

Mr Javid, the Home Secretary, earlier this week asked the MAC to consider if there was a case for regional salary thresholds for different parts of the UK. The SNP administration has warned the current minimum £30,000 threshold for all high-skilled migrant workers coming to the UK post-Brexit, could reduce eligible EU workers in Scotland by as much as 85 per cent.

With the clock ticking down to the close of the ballot of Monday July 22, the friction between the Johnson and Hunt camps is increasing.

Dominic Raab, the former Brexit Secretary and a key Johnson supporter, took to the airwaves after the former London Mayor pledged a “do or die” Brexit departure on October 31 while Mr Hunt dismissed it as a fake deadline.

Mr Raab asked: “This is the question for Jeremy Hunt: if he thinks October is a fake deadline, how long will this paralysis go on for and what conditions would…[he] accept for an extension?

Rory Stewart, the International Development Secretary and a Hunt supporter, queried Mr Johnson’s “do or die” remark, referring to Tennyson’s poem about the Charge of the Light Brigade, saying he hoped it was “not some sort of charge towards the guns".

After Liam Fox, the Trade Secretary and Hunt backer, rubbished Mr Johnson’s claim that there would be no tariffs in a no-deal outcome, Steve Baker, who is supporting his fellow Brexiteer, hit back, accusing the Cabinet minister of “ludicrously tilting at windmills”.

In a joint statement today, 18 Tory MSPs and three MPs come out for Mr Hunt, saying he has “proven to us he understands Scotland’s interests and will do whatever it takes to keep Scotland in the Union”.

In a tweet three MPs supporting Mr Johnson – Ross Thomson, Colin Clark and Douglas Ross – made clear “no candidate is more Unionist than the other” and added: “The real threat to the Union is failing to deliver Brexit by October 31 and allowing Jeremy Corbyn, propped up by Nicola Sturgeon’s SNP into No 10, agreeing to another divisive independence referendum.”

In other developments -

*The respected economic think-tank, the IFS, number-crunched Mr Hunt’s campaign promises - a £15 billion increase in defence spending alongside a £13bn corporate tax cut – and said they “would leave no scope to relieve pressure on other areas of public spending without tax rises or fiscal stance which risked putting debt on rising path”.

*Jo Swinson, the deputy Liberal Democrat leader, said at a Westminster hustings that a Johnson victory would be "disastrous for our country" but "the silver lining is, it's good for the Liberal Democrats" as he would be a "great recruiting tool" for the Lib Dems.

*During PMQs, the SNP’s Ian Blackford described Mr Johnson as the “most incompetent Foreign Secretary in a century…who has made a career out of lying” while be branded Mr Hunt the “most incompetent Health Secretary in our history…who writes books on privatising our NHS”.