Foreign Secretary Dominic Raab will head to the region around Afghanistan for talks about the rescue of those left behind in Kabul after the departure of the remaining foreign forces.

The Cabinet Minister said he would be leaving for the area on Wednesday after a combative grilling on the Government’s handling of the crisis in Afghanistan by the Foreign Affairs Committee.

Mr Raab revealed to MPs on the cross-party group that he would be heading “to the region” after the hearing, but did not say where exactly due to security reasons.

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. This indicates that talks are likely to include Pakistan.

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.

Ministers have declined to give an update on the numbers of Afghans who have not been airlifted out of Kabul by the RAF. Mr Wallace previously estimated that up to 1,100 eligible Afghans would not be evacuated before the exit of foreign forces.

Mr Raab told the Commons committee: “We’re always very careful about signalling travel movements because of the security implications.

“But I can tell you I’m leaving after this committee to go to the region.”

Mr Raab appeared to indicate he was going to Pakistan during the trip when asked by committee chair Tom Tugendhat “is this your first trip to Pakistan?”

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

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.

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

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.”

Mr Raab said the central assessment of the UK Government was that Kabul was “unlikely” to fall in 2021, despite it ultimately being taken by the Taliban in the middle of August.

“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,” he said.

Mr Raab blamed an “optimism bias” surrounding intelligence when asked by Bob Seely, a Tory MP who served in Afghanistan, why the UK got it so “badly wrong”.

The Foreign Secretary repeatedly refused to indicate when he departed for his controversial Crete holiday, for which he was widely criticised because the Taliban were seizing back control of Afghanistan.

Labour MP Chris Bryant asked whether he was already on the Greek island on August 11 when the US was saying 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.”

He said that the UK started planning for a possible evacuation of Afghanistan in June.

“We started planning in June for the contingency of an evacuation and therefore a full drawdown of the embassy,” the minister told MPs.

Mr Raab 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.

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”.

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

Mr Raab said he has 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.