Lawyers acting for three Afghan interpreters who have worked with British forces have launched a legal challenge against the government's decision not to allow them to settle in the UK.
The interpreters face the threat of Taliban attacks in their homeland and their supporters claim that they have been denied assistance offered by the Government to Iraqis in similar circumstances.
Law firm Leigh Day firm have issued proceedings against the Foreign Secretary and Defence Secretary, claiming their situation is no different to the Iraqis and that they should be afforded the same benefits in accordance with the government's obligations under the Equality Act 2010.
Iraqis who qualified for assistance were eligible for a one-off package of financial assistance or exceptional indefinite leave to enter the UK, outside normal immigration rules.
The family of one of the men involved in the challenge, known as Abdul for security reasons, has already received threats, Leigh Day says.
His father reported receiving a phone call from an unknown male calling him and "infidels spy" and adding: "We have found your place. Very soon you will see your punishment."
Another, Mohammed, who was recently granted asylum, was seriously injured by an bomb in 2007 while on patrol with British and Afghan forces.
Leigh Day said he received death threats and was physically attacked before he fled to Britain although his request for a visa was refused.
Rosa Curling from Leigh Day, who is representing the three men, said: "The recent threats made against Abdul and his family further underline the very real dangers these men and their families face as a direct result of their work, and incredible bravery, in support of the British forces in Afghanistan.
"The Government has a duty to ensure that they are not left exposed to the very real dangers posed by the Taliban. The failure by the UK government to extend to the Afghan interpreters the resettlement package offered to Iraqi interpreters is unlawful and discriminatory."
News of the legal challenge came as campaigners prepared to deliver a petition calling on the Government immediately to grant asylum to Afghan interpreters.
The petition, signed by more than 69,000 people, will be delivered to the Foreign Office this afternoon by campaigners including former British servicemen, pressure group Avaaz said.
Aimed at Foreign Secretary William Hague, it states: "As concerned UK citizens, we call on you to immediately grant asylum to all Afghan nationals who have worked as translators for British forces in Afghanistan.
"Risks to their lives are growing daily as the UK starts to withdraw; we cannot abandon them and we must act now. Their fate is in your hands."
The move comes after Prime Minister David Cameron on Wednesday said Afghan interpreters who worked with the British armed forces should, where possible, stay on in their country to help rebuild it after years of conflict.
Mr Cameron said that "in extremis" - where individuals were under direct threat of reprisals if they remained - they should be allowed to come to the UK, but he believed most should stay on to join the work of reconstruction and he had asked officials to draw up a "really generous" financial package for those who chose to remain.
He said: "I don't think we should turn our backs. I think there are two things we should do. One is to make sure that in extremis of course people can apply to come and live in the UK and we should have a fair system for doing that.
"But I do think that when we think of all that we have spent and all the cost in money and human lives we have put into Afghanistan, we should do everything we can to encourage talented Afghans to stay in their country and contribute to it."