Vicar of Baghdad Canon Andrew White has urged Westerners not to join Christian militia in Iraq because Christians are "hopeless at fighting".

Canon White, in Tennessee in the US on a fundraising mission for his charity, the Foundation for Relief and Reconciliation in the Middle East, said he knew of a number of Christians who wanted to join anti-ISIS militia.

He urged them to think again, telling Christian Today: "The fact is that Christians are universally hopeless at fighting, let alone fighting ISIS."

He cited the story of one of his Iraqi Christian guards in Baghdad. "I said to him, 'What would you do if ISIS were coming towards us?' He said, 'I would rip off my uniform and run.' So I said, 'Why do you do this job?' He said, 'I do it because I need the money.'

Canon White said: "Christians are no good at being soldiers. If going to join the new militia makes them feel good, great. But it will achieve absolutely nothing. We are dealing with an evil, evil regime as we saw in Libya with the beheadings of the Coptic Christians. There is very little that any Iraqi Christian or British Christian can to do help. The best thing they can do is stay at home."

Any action should be what is already happening, said Canon White, who is helping to rehouse, feed and educate thousands of Christians who have fled to Jordan, where he has just set up a school for 300 children.

He was speaking after Isabel Coles reported for Reuters from Iraq about Westerners going to Iraq to fight ISIS.

She described Brett, 28, who carries the same thumb-worn pocket Bible he did while deployed to Iraq in 2006 – a picture of the Virgin Mary tucked inside its pages and his favorite verses highlighted and has Saint Michael, the archangel of battle, tattooed across his back of a US army veteran. He recently returned to Iraq and joined a Christian militia fighting Islamic State in what he sees as a biblical war between good and evil.

"It's very different," he said, asked how the experiences compared. "Here I'm fighting for a people and for a faith, and the enemy is much bigger and more brutal."

She reported that thousands of foreigners have flocked to Iraq and Syria in the past two years, mostly to join Islamic State, but a handful of idealistic Westerners are enlisting as well, citing frustration their governments are not doing more to combat the ultra-radical Islamists or prevent the suffering of innocents.

The militia they joined is called Dwekh Nawsha – meaning self-sacrifice in the ancient Aramaic language spoken by Christ and still used by Assyrian Christians, who consider themselves the indigenous people of Iraq.

A map on the wall in the office of the Assyrian political party affiliated with Dwekh Nawsha marks the Christian towns in northern Iraq, fanning out around the city of Mosul.

Dwekh Nawsha operates alongside Kurdish peshmerga forces to protect Christian villages on the frontline in Nineveh province.

She also reported that some westerners were turned back from the frontline on Friday by Kurdish security services who said they needed official authorisation.