Dominic Raab is facing new calls to quit after claims that he defied a call to return from his luxury holiday in Crete to deal with the Afghanistan crisis and stayed for two more days.

It is reported that the beleaguered foreign secretary was told by a senior Downing Street official to return to London immediately on Friday 13 August as the Taliban advanced on Kabul.

But it is claimed he “nobbled” Boris Johnson and was assured by the prime minister that he could remain at his five-star beach holiday until Sunday and eventually returned in the early hours of Monday morning.

Responding to the reports, in The Sunday Times and Mail on Sunday, the SNP’s Westminster leader Ian Blackford tweeted: “This makes it impossible for Dominic Raab to stay in office.

“What we thought was a grave error of judgement is now seen as obstinacy and pig headedness when faced with demands to return to work. He must be sacked by Boris Johnson this evening. This is unforgivable.

And Labour’s shadow home secretary Nick Thomas-Symonds tweeted: “This is shameful. A vacuum of leadership at the heart of government.

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“To knowingly stay on holiday in the grips of an international crisis – when our troops are putting their lives at risk – is unforgivable.

According to The Sunday Times, a senior government official said: “Raab was told to come back on Friday. On Sunday there was a sense of disbelief among everyone at the most senior levels in No 10 that he wasn’t there.

“He seems to have nobbled Boris after he was told to come back.”

But the Sunday Times reports that Mr Raab’s allies say he was told to “begin the process of coming home”. One ally added: “In discussions with the prime minister it was agreed he would come back on Sunday.”

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The Mail on Sunday quotes a source saying: “There is no doubt that Raab was told to come back on that Friday. There was then a significant amount of surprise when he appeared on the Cobra on the Sunday down the line from Crete. He must have nobbled Boris and asked for permission to finish his holiday.”

The Mail on Sunday also quotes a close ally of Mr Raab insisting that No 10 had not ordered him to return on the Friday.

The ally told the paper: “The suggestion was that he should make plans to come back. They said that if things get worse then he needed to be ready to come back at a moment’s notice. He then talked it through with the PM and it was agreed that he would come back on Sunday.”

The same ally also strongly denied reports that Mr Raab had spent most of last Sunday on the beach at the five-star Amirandes Hotel, which boasts on its website: “A unique hotel built around water allures you at every turn.”

The ally told the Mail on Sunday: “That is just not true. He based his family on the beach in a gazebo precisely so that he could go back and work at the hotel, while checking in on them every now and again.”

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As he faced further calls to quit, a defiant Mr Raab told the Mail on Sunday he had enjoyed support from Conservative MPs and denied that there was pressure from within his party to resign.

“I’ve not heard any of my Conservative colleagues call for me to resign, but I have had a wave of support,” he told the paper. “There is no doubt that, like all countries, there is a measure of surprise at the rapidity of the Taliban takeover.

“But as the foreign secretary travelling around the world, whether I am on leave or I’m travelling for work purposes, I am always set up to be able to grip things.”

Asked about the reports, a Downing Street spokesperson said: “We don’t comment on private conversations”.

Sky News has also approached the Foreign Office for comment.