Boris Johnson has said it is an “illusion” to think Britain alone could have prevented the collapse of Afghanistan after the US withdrew its forces.

As MPs returned to Westminster for an emergency sitting of Parliament, the Prime Minister denied the Government had been unprepared for the Taliban takeover at the weekend.

He told a packed Commons chamber the priority now is to evacuate remaining British nationals and their allies.

The Government has faced intense criticism – not least from Tories – following the rapid unravelling at the weekend of the Western-backed government of President Ashraf Ghani in the face of the Taliban advance.

Mr Johnson said when ministers came to consider the UK’s options after the US announced its intention to withdraw, they came up against the “hard reality” that there was no will among allies to continue without the Americans.

“The West could not continue this US-led mission, a mission conceived and executed in support of America,” he said.

“I really think that it is an illusion to believe that there is appetite amongst any of our partners for a continued military presence or for a military solution imposed by Nato in Afghanistan. That idea ended with the combat mission in 2014.

“I do not believe that today deploying tens of thousands of British troops to fight the Taliban is an option that, no matter how sincerely people may advocate it – and I appreciate their sincerity – but I do not believe that that is an option that would commend itself either to the British people or to this House.

“We must deal with the position as it is now, accepting what we have achieved and what we have not achieved.”

There were cries of disbelief from MPs when Mr Johnson rejected claims that the events of the weekend had caught the Government unawares.

He said planning had been under way for a number of months and that a decision to commission an emergency handling centre at Kabul airport was taken two weeks ago.

“I think it would be fair to say that the events in Afghanistan have unfolded and the collapse has been faster than even the Taliban themselves predicted,” he said.

“What is not true is to say the UK Government was unprepared or did not foresee this.

“It was certainly part of our planning – the very difficult logistical operation for the withdrawal of UK nationals has been under preparation for many months.”

The situation has stabilised since the weekend but it remains precarious

Mr Johnson said the priority was to evacuate as many of the remaining UK nationals and Afghans who had worked with the British in the country as quickly as possible.

While the Taliban were currently allowing the evacuation to continue, he said it was unclear how long that would remain the case.

“The situation has stabilised since the weekend but it remains precarious, and the UK officials on the ground are doing everything that they can to expedite the movement of people,” he said

“At the moment it would be fair to say that the Taliban are allowing that evacuation to go ahead.

“The most important thing is that we get this done in as expeditious a fashion as we can and that is what we are doing.”

Mr Johnson said the Government had so far secured the safe return of 306 UK nationals and 2,052 Afghans, with a further 2,000 Afghan applications completed and many more being processed.

He acknowledged the sacrifice of the British forces who had served in the country since 2001, and said he was committed to working with allies to ensure it did not again become a centre of international terrorism.

“Even amid the heart-wrenching scenes we see today, I believe they should be proud of their achievements and we should be deeply proud of them,” he said.

“They gave their all for our safety and we owe it to them to give our all to prevent Afghanistan from once again becoming a breeding ground for terrorism.”

Labour leader Sir Keir Starmer said there had been a “failure of preparation” by the Government for which Mr Johnson bore a “heavy responsibility”.

He said the Prime Minister was in a position to give a lead on the international stage but had failed to do so.

“The desperate situation requires leadership and for the Prime Minister to snap out of his complacency,” he said.

“We do not turn our backs on friends at their time of need. We owe an obligation for the people of Afghanistan.”

Overnight the Government announced plans to resettle 20,000 vulnerable Afghans – particularly women and girls – with 5,000 arriving in the first 12 months.

The plan drew criticism from some MPs that it was not generous enough but Home Secretary Priti Patel said it was important to have the right support in place first.

“We cannot accommodate 20,000 people all in one go. This is an enormous effort. We can’t do this on our own,” she told Sky News.

In the meantime, she said a separate scheme to resettle 5,000 interpreters and other local staff who had worked with the British was being expanded.

“There could be up to 10,000. We are expanding categories of people,” she said.

“We are working with partners on the ground to identify these individuals.”