SCOTTISH Tory MPs have been urged to “come out of hiding” and submit letters of no confidence in Boris Johnson to add to the rising number of party colleagues who have formally called for him to go.

Former minister Nick Gibb became the latest Tory to submit his letter in the wale of the Downing Street party scandal saying his constituents were “furious about the double standards”.

Meanwhile, it was reported ­yesterday a photograph of ­Johnson ­holding a beer at his lockdown ­birthday ­gathering has been handed to ­police investigating the events held at ­Number 10 during lockdown.

Conservative MP Conor Burns had previously defended Johnson over this gathering saying he had been “ambushed with a cake”.

The Prime Minister was also rocked by a string of resignations by five of his aides last week. Yesterday he announced staffing changes to

No 10, with Chancellor of the Duchy of Lancaster Steve Barclay ­becoming chief of staff and journalist Guto ­Harri joining Downing Street as ­director of communications.

SNP Westminster Deputy ­Leader Kirsten Oswald said: “Boris ­Johnson has broken the rules, misled ­Parliament, and is completely unfit for office. It’s time for Scottish Tory MPs to finally come out of hiding and submit their letters of no confidence.

“At a time when Tory MPs in ­England are calling for the Prime Minister to go, and Downing Street staff are quitting in protest, it beggars belief that the feeble five are enabling him to stay.”

Scottish Secretary Alister Jack is among those who have given their support to Johnson, while former Tory vice-chair Andrew Bowie said the Prime Minister should consider his position but he would wait to see “what the facts were”.

Oswald said the failure of the ­ Scottish Tory MPs to call for Johnson to quit was undermining the position of and “snubbing” leader Douglas Ross, who has called for the Prime Minister to stand down.

She added: “Despite being ­repeatedly overlooked for promotion, humiliated by the Prime Minister, and their Scottish Tory leader being dismissed as a ‘lightweight’ by their Westminster bosses, it seems they are still clinging to the hope of being given a ministerial job if they remain loyal.It’s time they showed some ­backbone and stood up for their constituents, instead of always putting their own careerist ambitions first.”

The number of MPs who have called for the PM to go to is now 15 – although not all have formally communicated this to chairman of the 1922 Committee, Sir Graham Brady.

A confidence vote will be triggered if Sir Graham receives letters from 54 MPs, 15% of the parliamentary party, calling for a poll.

Tory MP for Wimbledon Stephen Hammond has said he is “considering very carefully this weekend” whether he still has confidence in the Prime Minister and it “certainly looks like” the beginning of the end.

He told BBC Radio 4’s Week In Westminster yesterday he would be “reflecting on the  events of the week, reflecting on the fact that my constituents and I and almost all of the country obeyed rules, and there seems to be a group of people who haven’t”.

He said he had not yet put a letter into Brady, but added: “I think I’m making it very clear to you that I am considering very carefully over the weekend, what are the next steps.

“I think all Conservative ­colleagues, all of whom I know, are in it for trying to do the best for their constituents, and the country will be wrestling with their consciences this weekend.”

Speaking to BBC Radio Scotland’s Good Morning Scotland yesterday Sir John Curtice, professor of politics at Strathclyde University, said: “It is pretty clear that until the Metropolitan Police have reported and we then get the full version of Sue Gray’s ­report, that it just as looks this story is going to continue to run and run.”

He said the fundamental problem for Johnson was that his account of events was for the most part “simply not believed”, but one silver lining for the Prime Minister is that some Conservative voters have not yet ­concluded he should resign.

But Curtice added: “A Prime ­Minister, a party leader who is in a situation where two-fifths or more of those who voted for you only two years ago now think you should go is certainly not a very strong position when you are trying to persuade your MPs to allow you to stay in office.”