Boris Johnson will tell MPs that he will use “every economic, political and diplomatic lever” to help Afghans left behind by the British as he looks to defend his handling of the withdrawal from the country.

The prime minister will reiterate the pledge in the House of Commons on Monday, when parliament returns from its summer recess to examine the crisis in Afghanistan.

Both Mr Johnson and Foreign Secretary Dominic Raab have faced criticism over the withdrawal of British forces from the country following the rapid takeover by the Taliban.

Please use Chrome browser for a more accessible video player

Thousands of Afghans who worked with or assisted foreign forces, their families and other vulnerable groups are thought to have been left behind when troops left the country for good last month.

There are also warnings that the UK could be facing a raised terror threat if extremism is allowed to grow again under the Taliban.

In a week marking the 20th anniversary of the 9/11 attacks in New York, which was one of the turning points in the war on terror, and led to troops entering Afghanistan, Mr Johnson will say he will “use every economic, political and diplomatic lever to protect our country from harm and help the Afghan people”.

He is also expected to reveal details about the new resettlement programme for Afghans coming to the UK in the coming years.

As well as that, he will also use his speech to thank the 150,000 British servicemen and women for their work in Afghanistan over the past 20 years.

Downing Street has said that prime minister will also announce £5 million more in funds to help military charities support veterans’ mental health, with the aim of ensuring that “no veteran’s request for help will go unanswered”.

Follow the Daily podcast on Apple Podcasts, Google Podcasts, Spotify, Spreaker

Mr Johnson will be facing MPs for the first time since parliament was recalled to debate for the day on 18 August in the wake of Kabul’s fall.

Head of the armed forces Sir Nick Carter said on Sunday that “everybody got it wrong about the pace of the Taliban’s march recapture of Afghanistan” but added there was not a failure in military intelligence.

Speaking on the BBC’s Andrew Marr Show, he said: “The first scenario I think also would’ve said is it was entirely possible that the (Afghan) government wouldn’t hold on that much longer.

“Indeed, many of the assessments suggested it wouldn’t last the course of the year and, of course, that’s proven to be correct.”

Mr Raab was holidaying in Crete when Kabul fell, and previously argued that it was the assessment of the military and the wider intelligence community that it was “unlikely” that “Kabul would fall this year”.

Please use Chrome browser for a more accessible video player

Sir Nick said “there’s been a lot of talk about a failure of intelligence” but that he said back in July that “there are a number of scenarios that could play out and one of them certainly would be a collapse and state fracture”.

Among those evacuated from Kabul by the British forces include more than 8,000 former Afghan staff and their families.

However, around 1,100 Afghans that were deemed eligible to leave were thought to be left behind – but that figure will fall short of the actual number the UK wants to help.