Foreign Secretary Dominic Raab has said UK intelligence indicated Kabul was “unlikely” to fall this year, as he prepared to head to the region around Afghanistan for evacuation talks.

The Cabinet minister indicated on Wednesday that he would visit Pakistan during diplomatic efforts to help rescue those left behind after foreign forces left Kabul.

Mr Raab said he would be departing on Wednesday following a combative grilling by MPs over the Government’s handling of the crisis during an emergency session of the Foreign Affairs Committee.

He said he could not determine how many Afghans were left behind when the RAF departed Afghanistan but admitted they included guards who had secured the British embassy in Kabul.

There was sustained questioning on how the UK failed to predict the speed in which the Afghan government would fall to the Taliban, which ultimately seized Kabul on August 15.

Mr Raab said: “The central assessment that we were operating to, and it was certainly backed up by the JIC (Joint Intelligence Committee) and the military, is that the most likely, the central proposition, was that given the troop withdrawal by the end of August, you’d see a steady deterioration from that point and it was unlikely Kabul would fall this year.”

The minister partly blamed an “optimism bias” surrounding the UK’s assumptions when asked by Bob Seely, a Tory MP who served in Afghanistan, why Britain got it “so badly wrong”.

Mr Raab revealed to the cross-party group that he would be heading “to the region” after the hearing, but declined to say where exactly due to security reasons.

But he went on to indicate he was going to Pakistan during the trip when asked by committee chairman Tom Tugendhat: “Is this your first trip to Pakistan?”

“I’ve been to Pakistan before but not as Foreign Secretary,” the minister responded.

It is understood his diplomatic efforts will centre on how to get Afghans and any remaining British nationals out of the region through third countries.

The Prime Minister’s special representative for Afghan transition, Sir Simon Gass, has already travelled to Qatar to meet “senior Taliban representatives” about allowing people to leave Afghanistan.

And MI6 chief Richard Moore has reportedly held talks with the Pakistan military on Afghanistan in recent days.

This is the single biggest foreign policy disaster the UK has faced since Suez

Mr Raab was unable to say how many Afghans who are vulnerable under Taliban rule because they aided Britain’s efforts in Afghanistan were left behind.

When grilled on the numbers, the minister said: “I can’t give you a definitive answer.

“I’m not confident with precision to be able to give you a set number, but I am confident that the Prime Minister is right, that we’ve got the overwhelming number out.”

But the Foreign Secretary admitted that some of those left behind included Afghans who worked as guards at the British embassy in Kabul.

“We wanted to get some of those embassy guards through but the buses arranged to collect them, to take them to the airport, were not given permission to enter,” he said.

More than 8,000 former Afghan staff and their family members eligible under the Afghan relocations and assistance policy (Arap) were among the 15,000-plus people evacuated by the UK since August 13.

Mr Raab has said the number of UK nationals left behind is in the “low hundreds”.

Defence Secretary Ben Wallace has described the continuing evacuation efforts as “Dunkirk by WhatsApp”, with officials scrambling to contact Afghans who worked with the British military effort to help relocate them and their families.

Mr Wallace previously estimated that up to 1,100 Afghans who had been deemed eligible would not be evacuated before the exit of foreign forces.

In front of the committee, Mr Raab said that the UK started planning in June for a possible evacuation of Afghanistan, before coming under sustained questioning over his holiday to Crete in August.

He repeatedly refused to indicate when he departed for the controversial trip, over which he was widely criticised because he remained there while the Taliban were seizing back control.

Labour MP Chris Bryant asked whether he was already on the Greek island on August 11 when the US was warning the group was likely to take power.

Mr Raab repeated he “would not have gone away, with the benefit of hindsight”, before insisting: “I am not going to start adding to, frankly, the fishing expedition beyond the facts that I have articulated and the fulsome statement and having answered questions on this continuously.”

But he said he did not consider resigning over the crisis despite demands from Labour.

“No, I considered getting on with the job of what has been a Herculean task of getting 17,000 people out,” he said.

Mr Raab ordered a “full review” of the closure of the British embassy in Kabul after documents identifying Afghan workers and job applicants were found after the building was abandoned.

Mr Tugendhat, a senior Tory MP who served in Afghanistan, said he continues to believe “this is the single biggest foreign policy disaster the UK has faced since Suez”.

“I am afraid I struggle with the Suez analogy but I understand what you are really searching for is to learn the lessons and even more generally find a path forward for Afghanistan,” Mr Raab replied.

Following the committee hearing, Labour shadow foreign secretary Lisa Nandy described Mr Raab’s performance as “a staggeringly poor showing”.

She added: “Despite his own department’s clear warnings weeks before Kabul fell, the Foreign Secretary was asleep at the wheel. He could have stepped up the evacuation, issued warnings to British nationals and increased resources in his department. Instead he chose to go on holiday.

“Today’s committee session was a moment for humility and accountability, a chance to take responsibility for the chaotic failures that brought us to this point. Instead, he refused to apologise to troops who had to fly into danger to do a dangerous and difficult job because he hadn’t done his.”