A Dutch academic and expert in migration has called for better vetting of new arrivals, claiming 50 million Muslims around the world are prepared to accept the use of violence in “defence” of their religion and ideology.

Professor Ruud Koopmans, a former supporter of the left-wing Dutch Green party, said of the 1 billion adult Muslims in the world, “half of them [500 million] are attached to an arch-conservative Islam which places little worth on the rights of women, homosexuals, and people of other faiths”.

Speaking to RP-Online, he said around 50 million of the half-a-billion ultra-conservatives were in some way prepared to support violence in the name of Islam.

“They support the radicals, they encourage them and provide them shelter or simply keep their mouths shut when they observe radicalisation”, explained the Director of the Research Unit on Migration, Integration, and Transnationalisation at the Berlin Social Sciences Centre.

His 50-million estimate was likely to be “an understatement”, he said, citing studies showing that some eight per cent of German Muslims agreed with the use of violence against “infidels”.

In his own country, the Netherlands, he claimed 11 per cent of Muslims agreed with the statement: “There are situations in which it is acceptable for me, from the perspective of my religion, that I use violence.”

The professor also cited a study by the American Pew Research Center, which in 2013 asked Muslims in several Islamic countries whether suicide attacks against civilians are justified to defend Islam. An average of 14 per cent surveyed said that such attacks were “often / sometimes” justified.

“If we were to apply the 14 per cent from the Pew study to all of the Muslims worldwide, we would have 140 million supporters of violence,” he said.

When asked if Christians were also prepared to use violence in the name of religion, the professor said he had found little evidence in support of this notion.

“I have indeed investigated the spread of religious fundamentalism and hatred of foreigners among Muslims and Christians in Europe. The results showed that both are much more common among Muslims,” he said.

The professor also said Western nations must be more cautious with their immigration and vetting policies. “We owe it to the Christian, Jewish, and non-fundamentalist Muslim refugees who fled because of hatred and intolerance,” he insisted.