Ruth Davidson backs Theresa May after resignations of David Davis and Boris Johnson

Ruth Davidson has backed Theresa May following the resignations of David Davis and Boris Johnson over Brexit, with the Scottish Tory leader warning the cabinet is bound by collective responsibility and that “if individual ministers can't sign up to that, then it is only right they are no longer part of the government”.

Johnson and Davis resigned barely 48 hours after the Cabinet appeared to have finally agreed its Brexit strategy, with Davis’s decision to quit quickly followed by the resignations of Brexit ministers Steve Baker and Suella Braverman.

Davis said the agreement struck by the Prime Minister's top team at Chequers last Friday "will make the supposed control by Parliament illusory rather than real".

Scottish Tory MSP Ross Thomson then warned that the agreement struck at Chequers “appears so diluted that we would be a vassal state”.

But, with pressure mounting on May’s leadership, both Davidson and the Scottish Secretary David Mundell backed the PM, with the Scottish Tory leader arguing, “At this vital time for our country's future, people across Britain want - above all - a UK government negotiating with one voice on the Brexit deal it seeks to achieve.”

She said: “As I said on Saturday, I believe that the Prime Minister's Chequers plan is a sensible compromise approach, which both respects the referendum result to leave the EU, while offering pragmatism on trade, skills and regulation.

“For Scotland, those proposals will provide business with frictionless access to the EU, ensure we leave the Common Fisheries Policy, and make clear there will not be a border in the Irish Sea.

“This all helps to bolster Scotland’s biggest and most important market, the UK internal market.

“I believe therefore that the Prime Minister deserves our support as she prepares for the upcoming tough negotiations with the European Union.

“I would urge colleagues to put their shoulders to the wheel in supporting the Prime Minister in that job.”

But SNP Westminster leader Ian Blackford said Boris Johnson “should have been sacked for being a national embarrassment months ago”.

He said: ‘’The government is now paralysed in its own Brexit chaos. It has taken just two days for the last two years of Tory infighting to finally unravel – and we still have to wait until later this week to see the full White Paper from the government but reports and leaks from Chequers present some serious questions on the Prime Minister’s approach.

‘’These proposals – if they even survive – at best represent a starting point, and a cherry-picking starting point at that. It is hard to believe that it has taken the Prime Minister two years to even put together a proposal – but these resignations show a government out of control.

‘’At this absolutely crucial moment the Tories should be focussed on the Brexit negotiations, but yet again they are all putting their own selfish political interest ahead of the interests of the country.

‘’As the UK inches closer to a cliff-edge no-deal scenario – which threatens enormous damage to jobs, investment and living standards across Scotland and the rest of the UK – we see a government in chaos, and a Prime Minister struggling to lead her party, never mind her government.’’