US and UK troops should have stayed in Afghanistan “to see it through”, Tony Blair has said, as he warned the decision to withdraw personnel could lead to a “security threat” at home.

The former Labour prime minister said while he has “enormous respect” for US President Joe Biden, the number of individuals deployed in the country “had been reduced to a much smaller level” by 2019 and UK troops “were in a position to hold firm for some considerable time”.

Mr Blair, who sent UK troops into Afghanistan 20 years ago when he was prime minister, also urged the UK and its allies to develop a “strategy” to deal with the Taliban to ensure “we don’t end up with a security threat”.

His comments come a day after he published a 2,700 word article on Afghanistan in which he referred to President Biden’s decision to withdraw troops as “imbecilic” and said the move was “tragic, dangerous and unnecessary”.

In the piece released on Saturday evening, Mr Blair warned that the UK has a “moral obligation” to maintain a presence in Afghanistan until “all those who need to be are evacuated” have left the country.

Mr Blair told reporters the decision by the Trump administration to withdraw troops from Afghanistan was made “for internal American reasons” and that “we could have held firm and succeeded”.

“This was not a situation we needed to be in,” the former prime minister told reporters, adding: “In the world we have today, you’ve got sometimes to commit for the long term.”

He continued: “The problem with what’s happened now is that it’s not just about the Afghan people and our obligation to them, it’s about us and our security.

“Because you’ve now got this group back in charge of Afghanistan. They will give protection and succour to al Qaeda, you’ve got ISIS, Islamic State already in the country trying to operate at the same time.

“You look round the world and the only people really cheering this decision are the people hostile to Western interests.”

Mr Blair also called on the UK government and its G7 allies to work together to ensure peace.

He urged leaders to “hold firm” against people who are hostile to Western interests, even when the decision to do so divides opinion.

“The Taliban will find that governing is a lot harder than they thought. The population of Afghanistan is different,” he said.

“There’s going to be a lot that we can still do but it’s important that we mobilise now after the disarray frankly of the last few weeks, that we mobilise as the leading countries and make it clear that we still understand we have an obligation in our own interests to try and resolve this situation and to put as much pressure on the government in Afghanistan as possible to make sure that we don’t end up either with a security threat in play for us or with the Afghan people losing the gains they’ve made over the last 20 years.”

Mr Blair also defended his decision to deploy troops 20 years ago following emotive comments made by Afghanistan veterans in recent days, saying UK personnel “went in there for very good reasons” and did not make any “sacrifices in vain”.

He told reporters that what was achieved in Afghanistan over the past two decades still “matters today” and that Britain’s involvement in Afghanistan has not been a “hopeless endeavour”.

“I think it’s really important that people realise this, the story of Afghanistan, the story of the Taliban takeover, it’s not over,” Mr Blair added.

“It is tragic what’s happened, I think it’s unnecessary, I think we’ve made a serious mistake in doing this in this way, but it isn’t over yet.”