The Defence Secretary voiced fears that al Qaida could return to Afghanistan as he laid the blame for the country’s latest turmoil at the door of former US president Donald Trump.

Britain and the US have agreed to send more troops in as the Taliban’s lightning advance through the country continues – gains that come only weeks before allied forces are due to withdraw.

Taliban insurgents are now estimated to hold more than two-thirds of Afghanistan and continue to press their offensive, having taken the country’s second and third largest cities, Kandahar and Herat, as part of a week-long blitz.

Afghan officials announced on Friday that the Taliban had captured Lashkar Gah, the capital of the southern Helmand province.

Cabinet minister Ben Wallace denied the plan to send 600 troops in to Afghanistan, announced on Thursday, was a last-minute decision, arguing that it was put in place “some months ago” in preparation for withdrawal alongside the US by September 11.

The short-term deployment, which comes as the US vowed to send 3,000 of its troops to Afghanistan, will be used to support diplomacy, help citizens leave the country and support the relocation of former Afghan staff as the Taliban continues to make in-roads.

Mr Wallace – who refused to rule out further ground attacks or air strikes if the situation worsens – admitted he is concerned that multi-national terror network al Qaida, the group behind atrocities such as the 9/11 attack on the World Trade Centre in New York, could “come back” as Afghanistan de-stabilises once again.

Herat in Afghanistan has been lost to the Taliban, which is now estimated to control two-thirds of the battle-torn country
Herat in Afghanistan has been lost to the Taliban, which is now estimated to control two-thirds of the battle-torn country (Hamed Sarfarazi/AP)

He told Sky News: “Of course I am worried, it is why I said I felt this was not the right time or decision to make because, of course, al Qaida will probably come back, certainly would like that type of breeding ground.

“That is what we see – failed states around the world lead to instability, lead to a security threat to us and our interests.”

The Defence Secretary said he thinks the deal signed between then-White House incumbent Mr Trump and the Taliban in Doha, Qatar, in February 2020 to withdraw from Afghanistan was a “mistake” – but argued the UK had no choice but to follow.

Since the deal was signed, Mr Trump’s successor, Joe Biden, has continued with the withdrawal timetable.

Mr Wallace said: “I was public about it that at the time of the Trump deal – with obviously the Taliban – I felt that that was a mistake to have done it that way, that we will all, as an international community, pay the consequences of that.

“But when the United States, as the framework nation ,took that decision, the way we were all configured, the way we had gone in meant that we had to leave as well.”

Former defence minister Johnny Mercer said the situation in Afghanistan was a 'world tragedy'
Former defence minister Johnny Mercer said the situation in Afghanistan is a ‘world tragedy’ (Liam McBurney/PA)

But former defence minister and Afghanistan veteran Johnny Mercer contested the idea that the UK cannot act alone in the central Asian country.

The Conservative MP said it is “deeply humiliating” to watch the situation unfold in Afghanistan, with US officials stating that the capital, Kabul, could fall within weeks.

He told BBC Breakfast: “Biden has made a huge mistake here, but also we have a role.

“This idea we cannot act unilaterally and support the Afghan security forces is simply not true.

“The political will to see through enduring support to Afghanistan has not been there and a lot of people are going to die because of that, and for me that is extremely humiliating.

“It’s a world tragedy and we are going to reap the repercussions of this over many years to come.”

Rory Stewart, a former international development secretary, said “we are going to end up with terrorists” as a result of the Taliban regaining its grip over the country.

“This is a horrifying group associated with terrorists, they have been backing suicide bombing in the areas they control, women are not going to school and it is a total betrayal by the United States and the United Kingdom,” he told Sky News.

The former cabinet minister said Britain and the US would have to “expect to take a lot of refugees” following major population displacement in Afghanistan, because “this is our fault”.