Boris Johnson is facing calls from a former head of the British Army to launch an urgent humanitarian aid operation in Afghanistan amid fears of a looming refugee crisis.

As the UK began an operation to extract its remaining nationals from the country, Lord Dannatt said there was still time to show Afghans they were not being completely abandoned.

Thousands of refugees fleeing the Taliban have been pouring into the capital Kabul as the militants continued their lightning advance across the country.

The collapse of Afghan government forces followed the decision of the Biden administration to withdraw all remaining US forces, prompting other allies – including Britain – to follow suit.

While Lord Dannatt said he shared the anger of many military veterans who served there at the way the country was being left to its fate, he insisted it was still not too late for the UK Government to act.

“It is okay to extract our British citizens. What about mounting a humanitarian operation in Kabul to look after some of the refugees, to build some camps, bring in some humanitarian supplies?” he told BBC Breakfast.

“At least let’s show to the Afghan government we are not completely abandoning them and that we still stand side by side with them. It is quite possible to do that.

“I think our Government should be thinking about that kind of response even though it has now pulled the plug on our wider military response.

“There may come a moment when our last troops have got to go but until that point, let us do what we can to help with the humanitarian crisis, even if we have given up helping on the military side.”

Labour leader Sir Keir Starmer said Mr Johnson should seek emergency meetings of Nato and the UN Security Council to develop a “joined-up” international response to the crisis.

“While the decision to withdraw soldiers from Afghanistan was not one made by the British Government alone, more can, and must be done to ensure this withdrawal does not result in a humanitarian crisis,” he said.

“We have an obligation to the people of Afghanistan and a responsibility to lead the international efforts over the coming days and weeks to support the Afghan government.”

The first of 600 British troops taking part in Operation Pitting to assist in the withdrawal of remaining UK citizens began leaving for Afghanistan on Friday.

They will also help with the relocation of Afghans who helped British forces when they were in the country and now face reprisals if they fall into the hands of the Taliban.

Boris Johnson said on Friday the current situation was the “inevitable logical consequence” of the decision by the Biden administration to withdraw all remaining US forces by the 20th anniversary next month of the original 9/11 terror attacks.

The Prime Minister insisted the sacrifices of the British armed forces who fought in the country had not been in vain, but said there was no question now of a “military solution” to halt the Taliban onslaught.

He said the Government would use whatever political or diplomatic levers it could – including the UK overseas aid budget – to try to ensure that Afghanistan did not become a breeding ground again for international terrorism.

However there was anger among MPs across the political spectrum at the way events had unfolded with calls for Parliament to be recalled from its summer break so they can discuss the crisis.