RUTH Davidson has lost control of her MPs.

At least four Scottish Tories in Westminster have rejected Davidson’s vision of an “open Brexit” and joined Jacob Rees Mogg’s shadowy European Research Group of right wing Brexiteers who are trying to push Theresa May towards a hard, extreme Brexit.

Colin Clark, Alister Jack, and Stephen Kerr, along with 59 others, signed up to a letter being sent to the Prime Minister demanding the government break their promise to the EU, and reject the “standstill” transition where the UK’s relationship with the EU effectively remains unchanged in the time between Brexit day in March next year and when that 21 month transition period is over.

“Any implementation period should be based on WTO principles,” the letter says. Before insisting that the UK has “full regulatory autonomy”.

Ross Thomson, the Brexit fanatic Tory MP from Aberdeen South, said he too supported the letter, though it wasn’t entirely clear why he hadn’t signed it.

It’s a blow for Davidson, who last June hinted that she would use her bloc of 13 Tory MPs to push for a softer Brexit.

May’s government was effectively saved by Davidson after the disastrous snap general election last year.

The Scottish party had succeeded where the party in the rest of the UK had failed and managed to increase the number of MPs.

May, who only has a majority of ten thanks to a deal with the DUP, was told that the 13 Scottish Tory MPs, would effectively act as a bloc.

At the time sources close to the Scottish Tory leader told Buzzfeed that it would be Davidson rather than May who would direct those MPs.

“If you take away the 13 seats that were won by Ruth Davidson, right now we couldn’t even be forming a coalition with anyone,” one party source told the website. “Theresa May and her team are fully aware of that fact.

“The change in dynamic now is, before, Ruth was respected but had no currency in the game. Now she can say ‘if I pull my 13 away you don’t have a majority’. It will be like that, it won’t be subtle, it will be a distinct group which will be at the disposal of the UK Conservative party when Ruth thinks it’s good for Scotland.”

They added: “Ruth’s stance on Brexit is clearly different – she signalled to May and the Brexit ministers that she needs to be in play,” said the source.

“She hasn’t fallen behind the PM and said ‘no matter how shit this deal is I’ve got your back’ – she’s made is very, very clear that there’s a different Scottish dimension to all of this and she needs to be in the room.”

Another source added: “Ruth knows she holds 13 cards and can use those to exert influence over the direction of Westminster policies. Where there is a difference of view, I fully expect the 13 to follow Ruth’s line – their loyalty will be to her in the first place.”

Yesterday, it became clear, that not all of their loyalty was to her.

Jack told the BBC that it would be wrong to think of Davidson as the real boss of him: “Well I hope that Ruth is supporting the Lancaster House speech, I’m sure she does. I’m sure she is, as all Conservatives are.

“We are a broad church. She is a very good leader. She does not tell us all how we have to think or tell us all how we have to vote.

“We vote with our conscience as a member of Parliament. And we will stand up for the things we believe in.

“And she hasn’t got a problem with that.”

Thomson tweeted: “I wholeheartedly back this letter of support to the PM which gives power to her elbow in these crucial negotiations to achieve a clean #Brexit. Out of the Single Market, out of the Customs Union and delivers a special economic partnership with the EU that works for the whole UK”

A Scottish Tory spokesman said all of the party’s MPs and MSPs are “united in wanting to deliver a successful Brexit for all of us in the United Kingdom and all support the prime minister in her efforts to do so.”

The four Tory MPs did not respond to The National’s request for a comment.

Tory MP Anna Soubry said the Prime Minister should “listen to British business” and not the “ideologically driven unicorn chasers” in the ERG.