Britain could be prepared to undertake lethal drone strikes in Afghanistan if the Taliban fail to prevent international terrorism taking hold in the country, the defence secretary said on Tuesday.

Ben Wallace was speaking as he showcased a £16m prototype of the remotely piloted Protector in Lincolnshire, making one of the first ever flights by a large drone capable of bearing missiles in the UK.

When asked if he was prepared to consider launching drone strikes in Afghanistan, Wallace said: “I’ll do whatever I have to do to protect citizens’ lives and our interests and our allies, when we’re called upon to do so, wherever that may be.”

Talk of using drones against terror groups operating in Afghanistan has increased following last month’s chaotic withdrawal, which also left hundreds of westerners and thousands more Afghans who had worked with the west stranded in the country.

Emergency airlifts finally resumed on Thursday, organised by Qatar. Thirteen Britons were among about 150 westerners evacuated to the country’s capital, Doha, the first evacuation flight since the US left Kabul’s airport last month and handed it over to the Taliban.

Many others, however, remain in the country. A car mechanic from Walthamstow in east London, who has lived in the UK for 18 years, told the Guardian: “I’m in hiding. I feel scared to go out,” and complained about the lack of help he had received from the British authorities. Unable to get on a plane from Kabul, he said he was prevented from using his British passport to cross the border to Tajikistan, Uzbekistan and Turkmenistan in the past few days.

For Britain to re-engage in combat operations in Afghanistan would normally require a fresh vote in parliament. But Wallace also hinted at using drones in situations that could permit military action in self-defence, although any such deployment could be controversial.

The cabinet minister said: “One of the options is to deploy anywhere in the world where there is an imminent threat to life, British life or our allies, where international law enables us to take action.”

Last month, the US launched a drone strike against what it said was a terror target in Kabul. But the Pentagon is now investigating what happened following reports from the Afghan capital that a family of 10, including seven children, were killed in a tragic error.

Critics say the use of drone technology presents increased ethical problems. Chris Cole of Drone Wars UK said the new drones “are being acquired to ensure that the UK can continue to intervene militarily overseas without the risk of having troops on the ground”. But he added the apparent killing of a family in Kabul demonstrated “such intervention hugely increases the risk to innocents on the ground”.

Britain has ordered 16 Protector drones at a cost of £260m, which it hopes to have in service by 2023 or 2024, as an upgrade to its existing fleet of nine Reaper drones, currently deployed against Islamic State in Iraq and Syria.

Capable of being loaded up with 16 missiles, the Protector has an operating range of 1,250 miles when armed, double that of the Reapers. They can fly on missions lasting up to 40 hours, loitering in the air to hunt for potential targets, piloted miles away from the battlefield at RAF Waddington in Lincolnshire.

Wallace tempered his comments about Afghanistan by saying he did not believe there was “a short-term” international terrorist threat capable of emerging from the country, where al-Qaida had been based in the run-up to the 9/11 terror attacks, despite attacks conducted by the local IS group in the country.

But he said that Islamist terror groups around the world were “taking inspiration from what they’ve seen in Afghanistan, whether that’s al-Shabaab and Boko Haram in Africa or Isis affiliates in other parts of the world” – and he argued that “the global terrorist threat has taken an uptick”.

The Protectors can also be flown over the UK, sharing civilian airspace, allowing the prototype to be test-flown from RAF Waddington from the beginning of the month. But defence chiefs said they would be primarily used for military purposes and were too expensive to deploy to monitor the movement of migrants over the Channel.