Said Musa, a 45-year-old Red Cross worker, has been told he will be executed within three days unless he converts back to Islam.

He has been in prison since being arrested for apostasy eight months ago after he was identified as one of the people who were baptised in a documentary that aired on Afghan television.

According to Barnabas Fund, Musa is yet to stand trial and no defence lawyer has come forward to defend him, some because of the death threats they have received.

Despite talks with the US Secretary of State Hillary Clinton and representatives of the French and German governments, President Karzai has not intervened to free Musa.

Barnabas Fund is calling for the release of Musa and other converts to Christianity being held behind bars, and has urged Western governments to put pressure on President Karzai to uphold the respect for human rights, including religious freedom, enshrined in the Afghan constitution.

“The constitution upholds international standards of human rights in theory, but in practice the government’s policy towards converts appears no different from that of the Taliban,” it said in an appeal.

“As long as the West continues to prop up the Karzai regime and refuses to demand tougher action by the Afghan government to uphold its international agreements, it is surely complicit in the persecution of converts to Christianity.

“This failure reflects a wider indifference among Western governments to the plight of Christians, and especially converts, in the Muslim world.”

Barnabas Fund criticised the European Union for failing to condemn recent attacks on Christians in majority-Muslim countries and hit out at the change of emphasis in the rhetoric of US President Barack Obama and British Prime Minister David Cameron, from appeals for “freedom of religion”, which includes the right to choose and change one’s faith, to simply “freedom of speech” and “freedom of worship”.

Dr Patrick Sookhdeo, international director of Barnabas Fund, said: “Said Musa’s plight can be seen as a test case for how Western governments are going to respond to the treatment of converts to Christianity in the Muslim world.

“I urge you to join us in putting pressure on them to use their influence to achieve for everyone the universal right to full freedom of religion.”

Click here to sign the petition: barnabasfund.org/save-afghan-converts-to-christianity/