Scottish Conservative leader Ruth Davidson has thrown her backing behind Theresa May amid a growing crisis over the prime minister's Brexit strategy.
Foreign Secretary Boris Johnson and Brexit Secretary David Davis have both quit Mrs May's cabinet over the issue.
But Ms Davidson said the plans set out by the prime minister were "a sensible compromise approach".
The SNP and Labour both said Mrs May had lost authority and her government become an "absolutely chaotic circus".
The UK government cabinet gathered at Chequers, the prime minister's country residence, last Friday to agree an approach to the Brexit talks.
There have been divisions within the Conservatives over how close the UK should be to the EU after leaving in March 2019. While Mrs May said a "collective" plan had been agreed on Friday, her government was quickly rocked by the resignations of Mr Davis and Mr Johnson - two of the leading voices in the Leave campaign.
Mrs May told MPs that she did not agree with the two ex-ministers about "the best way to honour" the result of the 2016 vote.
BBC political editor Laura Kuenssberg said sources had told her that either Mrs May "dumps" the plan signed off at Chequers or "another minister will go, then another, then another, then another".
Ms Davidson threw her backing behind Mrs May, saying people across the country wanted "a UK government negotiating with one voice on the Brexit deal".
And she took aim at Mr Johnson and Mr Davis, saying: "The prime minister made clear this weekend that collective cabinet responsibility must be observed on Brexit.
"If individual ministers can't sign up to that, then it is only right they are no longer part of the government.
"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."
'Out of control'
The SNP said Mr Johnson "should have been sacked for being a national embarrassment months ago".
Westminster leader Ian Blackford said: "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."
Scottish Labour said the Conservative government had "collapsed into chaos".
Shadow Scottish Secretary Lesley Laird said Mrs May was "in an unsustainable position", adding: "This isn't strong and stable - this is a complete Tory shambles".
With Mrs May's government propped up by the votes of 10 DUP MPs, splits in the Conservative benches raise questions about whether the Chequers plan - due to be formalised in a White Paper next week - could survive a Commons vote.
Scottish Secretary David Mundell was among those backing Mrs May's plan.
He said: "These are proposals which will bring significant benefits to Scotland and the whole of the UK, and I urge everyone to get behind them."
However, another Scottish Tory MP, Ross Thomson, said he was "deeply concerned" by the Chequers plan, saying it "appears so diluted that we would be a vassal state", adding that he was "proud" of Mr Davis and Mr Johnson.
He added: "The decisions we take now will shape Britain's relationship with the EU and the rest of the world for a generation. It's imperative we do Brexit right, no half measures."