Former military commanders and MPs with military service have criticised the UK's troop deployment to help Britons escape Afghanistan, with one describing it as an "admission of failure".
Defence Secretary Ben Wallace said on Thursday night that the UK would deploy 600 troops on a short-term basis to help an estimated 4,000 British citizens and others leaving the country.
It comes as the Taliban increases its grip, taking the major cities of Herat, Lashkar Gah, and Kandahar in the past 24 hours.
Thousands of Afghan civilians have fled their homes, many heading to Kabul to escape the fighting. But even there, they are not safe – there are fears that the Afghan capital could fall to the Taliban within weeks.
Lord Richards, a former chief of defence staff, told BBC's Newsnight: "It is a tacit – explicit, really – admission of failure – of a gross, dismal failure of geostrategy and of statecraft.
"I had hoped that we would hear from the Government an explanation for why we are in this position, and then an explanation for how they are going to avert this disaster.
"And all we have heard tonight is an admission of failure and a desire to pull people out.
"I'm almost ashamed that we are in this position."
Reflecting on the time of British forces in the country, Lord Richards told Forces News: "Broadly, while I don’t think it was a waste I am very disappointed that unnecessarily we have decided to turn our backs on a country that was slowly but surely making huge gains and those of us who served out there know what a difference we’ve made and we should be very proud of it.
"And the fact the Afghans, the vast majority of Afghans, are desperate for us to remain says it all."
Major General (Retired) Charlie Herbert, who served in Afghanistan and is now a campaigner for Afghan Interpreters, told Forces News it "feels like a bad dream."
"It feels like somebody's writing this awful disaster movie script that ends badly for us all," he told Forces News.
"It’s heartbreaking and what hurts so much is this is entirely avoidable.
"Leaving Afghanistan without an inclusive political settlement, as the Americans decided to do this summer, was ill-judged and everything that we’ve seen, all of the events unfolding, are as a result of that."
Tom Tugendhat MP, who served in Afghanistan and is chairman of the Foreign Affairs Select Committee, expressed his anger on Twitter, re-tweeting news of the US plan to send 3,000 of its own troops to help Americans leave safely.
He wrote: "A hasty exit is not a sign of success.
"Needing reinforcements to keep the door open as you leave is a sure sign of failure."
He said the decision to withdraw troops earlier this year was "like a rug pulled from under the feet of our partners".
Tobias Ellwood MP, who has also served in the British Army and is chairman of the Defence Select Committee, said on Twitter: "What would Churchill say?
"This is NOT our finest hour.
"What happened to GLOBAL BRITAIN and AMERICA IS BACK?
"The largest high-tech military alliance ever – defeated by an insurgency armed with mines, RPGs and AK47s. We can and must do better."
General Sir Nick Carter, the head of Britain's Armed Forces, said Afghanistan is already facing a "humanitarian tragedy".
Watch: Ex-military chiefs voice concern over Afghanistan amid Taliban gains.
The Chief of the Defence Staff added that the best Afghan President Ashraf Ghani could hope for is a "military stalemate" enabling him to seek a political compromise with the Taliban.
Former head of the Army Lord Dannatt told Forces News: "If this country [Afghanistan] becomes a failed state again, it provides a huge opportunity for other countries to maximise their influence for their own purposes.
"Our purposes were entirely honourable and good. I’m not sure you can say the same for Iran, Pakistan, Russia or China.
"Our Government must still, despite saying we’re removing our British citizens because that’s a responsible thing to do, we must go on supporting the Afghan Government, go on supporting that country every which way we can, short of military aid because we’ve ruled that out, in order to protect what we’ve achieved there and that thereby protects the legacy of the 457 of our service people who lost their lives there. That is worth fighting for."
Shadow Defence Secretary John Healey said: "We share widespread dismay that the security situation in Afghanistan is deteriorating so much faster than forecast.
"While our forces are withdrawing, we cannot walk away from the people of Afghanistan, so the UK should not be slashing aid, and ministers must push harder diplomatically with countries in the region to try to support a political process."