An Afghan national challenging the government’s treatment of fellow interpreters who worked for the British army claims to have identified two former colleagues being beheaded in footage on the internet.

Mohammad Rafi Hottak, 28, who was severely injured while working for British armed forces, is now living in Birmingham having fled his country in 2011 after receiving death threats. He said he was horrified to see images of two fellow allied translators with whom he lived in barracks in Kunar province being murdered by the Taliban.

The men, who Rafi believes are his friends Yahyah and Achikzai, are shown struggling as they are held down and their heads attacked with a handheld knife. A caption in Pashto describes them as spies.

Rafi, who is fighting for the right to allow his wife and three children to join him in Britain, believes the men were killed in 2006 by a Taliban commander. His lawyers, Leigh Day, revealed the footage to him last month.

“Yahyah and Achikzai were specifically targeted because they were interpreters for the allies. It still breaks my heart to think of what happened to these good-hearted, courageous men,” Rafi said.

A judicial review is expected to be heard next year on arguments on behalf of Rafi and two other Afghan interpreters that the British government’s scheme offered to locally employed staff by the British armed forces in Afghanistan is unlawful and inferior to the one offered to interpreters who worked with British forces in Iraq.

The Liberal Democrat peer Lord Ashdown and the former chief of naval staff Lord West have called for ministers to fulfil a “debt of honour” and accept about 450 Afghan interpreters who helped British servicemen in Afghanistan.

Following withdrawal from Iraq, local interpreters who had worked for the British for more than a year were offered a targeted assistance scheme, through which they could either accept a one-off package of financial assistance, exceptional indefinite leave to enter the UK or the opportunity to resettle in the UK.

But the Afghan redundancy programme offers only the chance to relocate to Britain for interpreters who worked with British forces in Helmand province for a minimum of 12 months and were employed in December 2012.

The offer is also inferior in other regards, the lawyers say. The hundreds who stopped work before the cut-off date but who also face death threats have to rely on a separate intimidation policy. Only one interpreter has been deemed to be at a sufficiently high risk to get a visa.

When shown the footage of the Taliban murder, he says he immediately recognised his friends Yahyah and Achikzai, with whom he had lived for four months in Allied barracks in Kunar Province. His friends went on to join a US mission in Uruzgan, Rafi said, but were then captured and handed to the Taliban.

“I cannot describe how I felt when I watched this video. I could not sleep properly, I had nightmares and I feel terrified for my family back in Afghanistan.

“This video shows the extreme violence and brutality which interpreters can face because of their work for foreign forces. These men were deliberately targeted by the Taliban,” he said.

Rafi, 28, was blown up in 2007 whilst on patrol with the British army and suffered severe injuries. He was finally given permission to stay in Britain in 2012 after initially having his initial application rejected.

He fled Afghanistan in 2011 after receiving death threats. His wife and three children remain there and have not been given permission to enter the UK – he has not yet held his three-year-old son.

The high court will hear arguments on behalf of Rafi and two other Afghan interpreters that the British government’s scheme offered to locally employed staff by the British armed forces in Afghanistan is unlawful.

Lawyers for the Afghan interpreters claim that not extending the scheme offered to Iraqis is “unlawful and discriminatory” under the Equality Act 2010, and that they should be afforded the same benefits.

The Afghan redundancy programme offers only the chance to relocate to Britain for interpreters who worked with British forces in Helmand province for a minimum of 12 months and were employed as of December 2012.

The hundreds who stopped work before the cut-off date but who also face death threats have to rely on a separate intimidation policy.

This has so far deemed only one interpreter at sufficiently high risk to get a visa.

Rosa Curling, a solicitor from Leigh Day said: “It is patently clear to us that the arrangements put in place by the UK government for these brave men, who fought alongside UK forces in Afghanistan, are completely inadequate. They do very little to protect former interpreters from the threats and attacks they are facing from the Taliban.”

A government spokesman said it was inappropriate to comment on the footage or the legal process. “We believe that our policies are honourable, fair and legally sound,” he said. “We fully recognise the contribution made by all locally employed civilians who worked with us in Afghanistan.

“A separate intimidation policy exists to keep current and former locally employed civilians safe in Afghanistan through a range of measures based on individual circumstances, ranging from day-to-day security advice to relocation within country. For those we judge might be in the most extreme circumstances, where there is a significant and imminent threat that cannot be mitigated in-country, we consider relocation to the UK.”