DAVID Mundell was allowed to rebel in a key Commons vote in the knowledge that he would not be called upon to resign or be sacked by Theresa May, The Herald understands.

The Scottish Secretary was one of four Cabinet ministers who defied the Prime Minister in a vote on Wednesday night. The others were Amber Rudd, Greg Clark and David Gauke.

Mrs May had, after pressure from senior colleagues, allowed a free vote on the UK Government’s own no-deal Brexit motion, which ruled out leaving the EU without a deal specifically on March 29 but kept open the option of a no-deal Brexit at any other time.

However, that motion was successfully amended to take the option of a no-deal off the table permanently.

Earlier this month, the four ministers, who abstained, privately went to see the PM in Downing St, demanding a no-deal outcome be ruled out completely. But Mrs May maintained that, without getting an agreement on a deal, no-deal remained the default option in law.

Mr Mundell, who represents Dumfriesshire, Clydesdale and Tweeddale, has repeatedly warned that a no-deal outcome would be catastrophic, economically and constitutionally, for the UK and Scotland.

His Tory colleague Stephen Hammond, one of 12 ministers who abstained in Wednesday night's key no-deal vote, said he had not been given permission to abstain by the whips but added: “I believe some colleagues may have been."

The Herald has been told Mr Mundell was reassured that he could abstain with impunity.

Under normal circumstances a minister who does not support the Government on a three-line whip would be expected to resign or be sacked. No 10, when asked about this, suggested that going into an opposition lobby to vote against the Government line was a resignation matter but was reticent about what, if any, sanction would be meted out to a minister, who abstained.

Mr Clark, one of the four Cabinet rebels, explained that the decision to whip the vote on the amended Government motion was made "very late in the day" without collective discussion and the abstainers believed they were acting "completely in accordance with long-standing Government policy".

Philip Hammond, the Chancellor, admitted there was "confusion" around the vote, adding: "I don't expect there to be mass sackings as a result of last night."

But, at Westminster, there were calls for the abstainers to be sacked.

Crispin Blunt, a Eurosceptic Conservative MP and former Prisons Minister, insisted if someone was in government, he or she should vote with the Government.

Asked if the PM should sack rebel ministers, the Surrey MP replied: "Well, obviously."

Nigel Evans, joint executive secretary of the 1922 Committee of backbench Conservative MPs, said Mrs May must regain control of her party after the ministerial rebellion.

"Her authority was openly defied by Cabinet ministers and other ministers," he declared.

"She needs to reassert her authority. We have to have collective responsibility in government, otherwise it just simply doesn't work.”

The Lancashire MP added: "Apparently, Cabinet ministers were confused last night as to whether they were on a three-line whip or not. Well, funnily enough, I received a text that told me on my phone that I was on a three-line whip. They received the same text. It's amazing that you can be a Cabinet Minister and still not know what a three-line whip text means.”

Sarah Newton, the former Work and Pensions Minister who resigned on Wednesday night after voting against the Government, argued that her fellow rebels should remain in the Government.

"I remain absolutely committed to ensuring that we leave the EU in an orderly way and still very much support the Prime Minister and her deal," stressed the Cornish MP.

She added: “It's essential the Prime Minister stays in position and that my colleagues stay in the Cabinet. My understanding is that they were offered the opportunity to abstain and they took that opportunity."