Afghanistan could once again become a base for international terrorism, according to a former senior UK military commander who has described the withdrawal of western troops as a “strategic mistake”.

As the Taliban continued to make sweeping territorial gains, Gen Sir Richard Barrons warned that attacks in Europe could be the outcome of groups re-establishing themselves in the country.

“I don’t believe it’s in our own interest – in making that decision to leave we’ve not only, I think, sold the future of Afghanistan into a very difficult place, we’ve also sent a really unfortunate message to the west’s allies in the Gulf and Africa and Asia,” he told BBC Radio 4’s The World This Weekend.

Sir Richard Barrons said the withdrawal of British troops suggested ‘we don’t have the stomach to see these things through’.

The former head of UK joint forces command, which linked the air force, Royal Navy and army, was speaking as three more regional capitals in Afghanistan fell to the Taliban, bringing the number to have fallen since Friday to five.

In their most significant gain, armed militants swept into Kunduz on Sunday, a strategic city close to the border with Tajikistan and an important political and military hub.

Barrons said that the withdrawal suggested that “we don’t have the stomach to see these things through and we would rather leave than ensure that a humanitarian or political crisis doesn’t occur”.

“We will run the risk of terrorist entities re-establishing in Afghanistan to bring harm in Europe and elsewhere. So I think this is a very poor strategic outcome,” he added.

Warnings about the potential terror threat to Britain and other states were echoed by Tory MP Tobias Ellwood, chair of the Commons defence committee, who used a column in the Mail on Sunday to condemn what he described as a “shabby withdrawal” that was “abandoning the country to the very insurgency that drew us there in the first place”.

“Unless we wake up to the reality of what is taking place, Afghanistan might once again become a terror state. This, remember, is the country that brought us 9/11,” he wrote.

Ellwood, a military veteran, called for the retention of a 5,000-strong coalition assistance force with sufficient ground, air and intelligence support to give the Afghan army the edge over the Taliban.

A UK government spokesperson said: “We recognise that the security situation in Afghanistan is serious, and reports of the escalating violence are extremely disturbing.

“We do not believe there is any military solution to Afghanistan’s conflict, and call on the Taliban to end their campaign of violence and engage in meaningful dialogue with the Afghan government.”