Nicola Sturgeon has said there will be a “widespread sense of relief” as the Prime Minister prepares to stand down.

Boris Johnson clung to power in the past 48 hours despite more than 50 resignations from his government, including Education Secretary Michelle Donelan after just over a day in the job.

The Prime Minister will stay on as interim leader until the Tories elect a new leader, which is expected to be before the party’s conference in October.

The First Minister pondered whether that was “sustainable”.

On Twitter she said: “There will be a widespread sense of relief that the chaos of the last few days (indeed months) will come to an end, though notion of Boris Johnson staying on as PM until autumn seems far from ideal, and surely not sustainable?”

She added that the Prime Minister was “manifestly unfit” to be Prime Minister, claiming that the events of this week shows the “Westminster system is broken”.

“For (Scotland) the democratic deficit inherent in Westminster government doesn’t get fixed with a change of PM.

“None of the alternative Tory PMs would ever be elected in Scotland. And in policy terms, it is hard to see what real difference hard Brexit supporting Labour offers.

“Independence only happens if a majority living in Scotland choose it – but there is no doubt it offers the real and permanent alternative to Westminster, and the opportunity to fulfil our potential at home and play our part as a good global citizen. It’s time for that choice.”

The Prime Minister is expected to make a statement on Thursday announcing his resignation.

Former Scottish Tory leader Baroness Ruth Davidson, however, said it was “arrant nonsense” the Prime Minister was going to stay on until the party conference.

“There’s no way he can stay on until October,” she said.

“It’s arrant nonsense to think he can. Someone needs to grip this.”

Scottish Labour leader Anas Sarwar said whoever replaces the Prime Minister will have been “complicit” in his administration.

“The entire country will breathe a sigh of relief that Boris Johnson is going,” he said on Twitter.

“But, let’s not forget that whoever replaces him is complicit. We don’t just need a change at the top, we need a change of Government.”

Mr Sarwar later described the Prime Minister as a “cheat, a charlatan, a man devoid of any principles or any values”.