A former Archbishop of Canterbury has accused the prime minister of failing to help Christians in the Middle East who are fleeing the atrocities of Islamic State.

Lord Carey of Clifton said David Cameron was guilty of turning his back on fellow Christians at risk of massacre in Syria and Iraq.

He has called for all concerned citizens to sign a petition launched by the Barnabas Fund to "welcome Christian refugees and give them priority as asylum seekers".

The Barnabas Fund is working with the Safe Havens project launched by Lord Weidenfeld, aged 95, a Holocaust survivor. The fund is in talks with other European countries on how best to resettle Christians facing persecution and murder by Islamic State in their historic homelands.

Last week, 42 Christian families were smuggled out of Syria to Beirut and then flown to safety in Poland. There will be more rescues to the Czech Republic and even Brazil but the UK has refused to accept any of the desperate refugees.

Lord Carey told the Telegraph: "Syrian and Iraqi Christians are being butchered, tortured and enslaved. We need the British Government to work with charities like the Barnabas Fund and others to evacuate those who are in desperate fear of their lives."

Lord Weidenfeld, who escaped from Nazi-occupied Austria in 1938 with the help of British Quakers, also told the newspaper: "Why is it that the Poles and the Czechs are taking in Christian families and yet the British government stands idly by?

"This mood of indifference is reminiscent of the worst phases of appeasement, and may have catastrophic consequences. Europe must awake and the Conservative British Government should be leading from the front.

"Most European governments, especially those that are Christian explicitly or implicitly, are failing in their duty to look after their fellow Christians in their hour of need."

The petition says that Christian communities in Syria and in Iraq are among the oldest in the world but that they now face "an existential threat to their survival."

It says: "They are being killed, enslaved and persecuted by so-called Islamic State and are forced to flee from their homes. Their homes are being destroyed and they have no safe areas in the region.

"The oppression and persecution of Christians, simply for their faith, is leading many Christians to conclude that they have no choice but to leave."

According to the Barnabas Fund, in this decade alone numbers of Christians in Iraq have fallen from 1.5 million to 300,000. In Syria about a quarter of the country's two million Christians have fled.

Dr Patrick Sookhdeo, of the Barnabas Fund, said: "With the rise of Islamic State we are seeing what looks set to become a 'genocide' of Christians in the Middle East, yet the UK has its doors firmly closed. So many British Christians have been in contact with us to tell us that they have a spare room or even a second home in which they want to welcome Syrian and Iraqi Christians. Yet our government seems determined to turn its back on some of the most vulnerable people in the world."

Canon Andrew White, the former vicar of the only Anglican church in Iraq, said: "I really think it is horrendous that the British have not offered refuge to these Christian refugees."

The Archbishop of Canterbury Justin Welby has stated publicly his concern for Christians in Syria and Iraq and offered his full support for them being given protection in the UK and in other Western countries.

Last month, the prime minister pledged to expand the number of Syrian refugees allow into the UK by a few hundred. He was criticised for not going far enough. A maximum limit of 1,000 has been set. This compares to 30,000 places offered by Germany.