An Afghan man who worked in the kitchen at the British embassy in Kabul for seven years has appealed to Boris Johnson to save him and his family from the Taliban, who he says are hunting him down.

“I am really scared, frightened. We have not been outside our house for four days. Every sound at the door makes us fear for our lives,” said Ahmad, who lives not far from the airport but is scared to travel there with his wife and three children, aged 22, 17 and 11.

“I was very proud to work with foreigners, we never expected this situation to happen,” he said. “We know the Taliban are so brutal. They will never forgive us for working with foreign governments. As a former employee of the British embassy for seven years, I want Boris Johnson to feel the pressure we are feeling because we worked for a foreign government. We request him to help as much as he can. Please help us get out.”

His wife said that if she knew working for the British and Americans “would have put our family in danger, we would never have worked with them.

“My 11-year-old daughter is crying all the time. There is the sound of shooting all the time because we are near the airport. We are very frightened and scared about our future. I haven’t slept for four days,” she said.

Ahmad, who asked that his real name was not published but who has shown his employment contracts to the Guardian, was working in a catering job at the embassy as an employee of G4S and then for security for the Americans.

Initially he fled to the Takhar region, where his parents live, but said the Taliban came looking for him. “Everyone knows I worked for foreigners. They have already come looking for me at my father’s house. They came to his door but I had already gone,” he said.

“I am very frightened. In Kabul right now the situation is very fragile and deteriorating. My son saw the Taliban shoot a young man in the chest and he died. All he was doing was staring at them because they look so different with their long hair and their beards. He was in his 20s.”

Ahmad said it did not matter to the Taliban that he was not senior or working with the army or in intelligence. “Any kind of work with the British or the Americans is seen as working with the enemy, the occupier,” he said, speaking through an interpreter at the Afghan Association in London.

Ahmad is one of many people whom the defence secretary, Ben Wallace, said on Thursday were in deep fear” of not making it to the airport. But Ahmad said he was hopeful. “Britain is a very powerful country. If there is a will, we hope they will find a way.”

His wife said: “We are trying everything we can to get out but right now we lock ourselves in our home. Right now I am so scared.”

Ahmad was contracted to G4S to work as a chef for the British embassy between 2007 and 2014 before he switched to a security firm working for the Americans.

He said the US company had already refused him help because he was a subcontractor. He had heard through Facebook about the UK home secretary, Priti Patel’s, offer to resettle vulnerable Afghans, he said, but questioned how British officials would be able to identify people such as him.

“So many people feel threatened. How can they contact us? We are too scared to contact other people. Even our neighbours could report us to the Taliban. Everyone knows we worked for foreign governments,” he said.

Ahmad’s case raises the question about what criteria the UK government is using for evacuation of those who have worked with them, and whether they will accept people who worked for them in earlier years.

It comes as the Guardian revealed more than 100 guards at the British embassy in Kabul were sacked from their jobs on Saturday night, and had been told they were not eligible for UK government protection because they were employed through an outsourced contract.

Karim Sharin, policy director of the Afghan Association of London, who facilitated the interview with Ahmad and was taking calls throughout the hour from desperate Afghans, said the evacuation of educated staff who worked for foreign governments could lead to a “second tragedy” for the country.

“Despite the Taliban assurances, people cannot trust what they say. If they go you will need another 20 years to build up an educated work force again. A brain drain will suit the Taliban because it will make it easier for them to rule,” he said.

A spokesman for the Foreign Office said: “We are making every effort to relocate eligible Afghan staff and their families who wish to relocate to the UK, and this commitment will endure. The team in Afghanistan, led by our ambassador and bolstered by additional diplomatic and military personnel, are working hard to get British nationals and former UK staff out of the country as quickly as possible.” They said the offer to staff was not “time limited”.