Islamic State has moved from persecuting Christians to attempting to exterminate them, a leading advocate for refugees has warned.

Dr Georgette Bennett, founder of the Multifaith Alliance for Syrian Refugees, said Islamic State is now targeting Christians as a group.

"We have now moved from Christians being persecuted to Christians being exterminated," she said. "We Jews – I am a Jew – we understand something about extermination. I think we recognise a genocide when we see it."

The Multifaith Alliance is a coalition of about 70 faith based groups including senior US Catholics, mosques, synagogues and churches.

Bennett, the daughter of Holocaust survivors, and Shadi Martini, who arrived at the US as a refugee from Aleppo in Syria and is senior policy adviser at the alliance, warned about the growing dangers of failing to respond adequately to the refugee crisis.

Speaking to Christian Today, Bennett warned that Britain is in danger of creating problems by not doing more to help those suffering in Syria.

"One of the dangers is that we are creating the very condition we fear the most by not rescuing children who have been out of school for years. We are leaving them very vulnerable to manipulation and radicalisation," she said. "By leaving millions of people in limbo for years we are creating a population that has nothing left to lose."

Bennett urged Churches to mobilise their members. "Both of our countries could be doing a lot more," she said.

"Religious institutions have vast constituencies – none vaster than Christianity. Given the vastness of the constituency, it means that the Church has enormous power to mobilise and to convene. If Church leaders use that power there is no end to what Christians can do to help in that crisis."

Martini said: "I look at Syria as a whole. Syria has been a country of mixed ethnicities and religions. I look at the situation as affecting all of Syria – Christians, Muslims, Yazidis – and see a horrific situation."

He said no one society or community is immune from the violence: "The best approach is to have peace. if you have peace it will be secure like it was for hundreds of years."

As a Syrian Muslim, he does not want Christians to disappear from Syria.

"The approach should be a balanced approach by everyone, to concentrate on the vulnerable, regardless of religion or ethnicity. ISIS is a criminal group that is committing a lot of atrocities. They are committing horrific crimes against everyone. A lot of people have been killed. Their killing machine kills everyone. It's a horrific group," he said.