Britain and its allies have no coherent plan to deal with the huge refugee crisis expected to follow the Taliban’s takeover of Afghanistan, a former cabinet secretary has warned. Mark Sedwill, a former ambassador to Afghanistan and senior adviser to two British prime ministers, said the emergency airlift out of Kabul had only helped “relatively small numbers” and greater pressures were likely to emerge as people fled overland. Speaking at a Policy Exchange thinktank event, Sedwill said that while the US decision to exit Afghanistan after 20 years could not be changed, it had a series of important consequences that required action from Britain and the west. “First, there will need to be a major humanitarian effort in and around Afghanistan. We will be very lucky indeed if there is not a really significant refugee crisis,” the former mandarin said, adding that the Taliban would have to run an “inclusive and wholly different government” from when they previously ruled, before the 2001 invasion. He said of the departure of foreign forces from Afghanistan: “This is, in my view, a bad policy, badly implemented. It is an act of strategic self-harm. “The Taliban’s victory in Afghanistan will undoubtedly fuel extremism and terrorism worldwide, whether or not it is directed from there.” The achievement of the emergency airlift, in which 114,000 people were evacuated from Kabul in just over two weeks “can’t and shouldn’t conceal that overall, we do not yet have a coherent policy and plan in place to deal with refugee flows out of Afghanistan”, Sedwill added. The UN refugee agency UNHCR has warned there could now be a further 500,000 Afghans crossing the border into neighbouring countries, on top of the 2.2 million who fled to countries such as Pakistan before the end of last year. Thousands of people recognised as having a firm or likely claim for resettlement in the UK were left behind in Afghanistan when the airlift ended – leaving Britain to call directly on the Taliban to allow others safe passage out of the country. Many other western countries are in a similar position. The foreign secretary, Dominic Raab, said on Thursday that evacuations might be able to resume from Kabul airport “in the near future”, as he began a tour of the region largely to solicit help in the evacuation of more people from the country. Late on Thursday night, the Foreign Office said it would make £10m of aid immediately available to the UNHCR to help provide shelters, sanitation facilities and emergency supplies to border refugee camps – and a further £20m to border countries that experience a significant increase in refugees, which could include Uzbekistan, Tajikistan and Turkmenistan. On a visit to paratroopers in Colchester on Thursday, Boris Johnson praised the British soldiers for their role in the UK airlift of more than 15,000 people from Afghanistan. The prime minister said: “When you look at the numbers that we’ve helped to come out … we’ve way exceeded the numbers we thought were eligible.” But Johnson acknowledged he did not have a clearer idea of the number of people yet to be evacuated. He said: “The answer is there are some – and we care for them very much, we’re thinking about them, we’re doing everything we can to help.” Last week the defence secretary, Ben Wallace, suggested that Afghans hoping to be evacuated to the UK might be better off heading to one of the country’s land borders, where Britain would accept claims made from neighbouring countries. But there is also growing concern that Afghans who cross the border to a third country who thought they could come to the UK may not be able to – and in a subsequent briefing for MPs on Monday, Wallace said those considering fleeing should “use their judgment” as to whether to cross the border. The resettlement entitlement for Afghan translators and others who worked directly for the British government is fixed – but the wider asylum rules for people who leave Afghanistan for a neighbouring country are yet to be determined. Sarah Olney, a Lib Dem MP, said: “I no longer know whether I should be advising people to go across the Afghan border. What if people cross the border thinking they were entitled to come to the UK and were refused.” Sedwill also warned that the goodwill of neighbouring countries could not necessarily be relied on, given the large numbers of Afghans who had already fled. “The neighbours really can’t absorb more,” he warned. Speaking in Qatar on Thursday, Raab said he had “good conversations” with the Qatari emir, Sheikh Tamim bin Hamad al-Thani, about the “workability” of evacuations resuming from Kabul airport for UK nationals and Afghans who worked with Britain. “I don’t think we’re yet able to say anything formal but that’s looking like it may happen at some point in the near future,” Raab told broadcasters. Qatar, with the possible help of Turkey, is hoping to help reopen the airport shortly, starting with internal flights. “There is no clear indication when it is going to be fully operational yet but we are working very hard and also engaging with the Taliban,” the emir added. Sedwill was the UK’s cabinet secretary and national security adviser from April 2018 to September 2020 and was Nato’s most senior official in Afghanistan a decade ago. But he was forced out of his last job by Johnson, with a promise that the UK would put him forward for the job of head of Nato in future. There were already an estimated 2.2 million Afghan refugees in neighbouring countries, according to UN figures, before the latest crisis, which has caused tens of thousands to head to the borders as the Taliban seized control. The UNHCR estimates that in a worst-case scenario, as many as 500,000 more refugees could flee the country to Pakistan, Tajikistan, Iran, Uzbekistan and Turkmenistan in the coming months.