British volunteers fighting against so-called Islamic State in Syria pose a domestic security threat to the UK, a think tank has claimed.

Since 2014, hundreds of people from Western countries, including the UK, have joined Kurdish rebel group YPG.

The Henry Jackson Society claimed the YPG was a front for a terrorist group and warned that those who join it could be drawn into terror activity at home. It said the government urgently needed to stop Britons joining the group.

The Home Office said those who return to the UK after taking part in conflicts in Syria or Iraq should expect to be reviewed by the police.

The Centre for the Response to Radicalisation and Terrorism, at the Henry Jackson Society, said the YPG was a subsidiary of the PKK, a “violent terrorist organisation” banned by the UK and the US.

The foreign affairs think tank said there was a danger those who fight for the group could participate in its “criminal-terror activities” or carry out “lone actor atrocities” when they return home.

The training they are given in firearms and explosives also poses a risk, the report said. Four British men have been killed fighting with the Kurds against IS and 29 Western volunteers have died in total.

Kurdish fighters on the ground in Syria have driven IS out of large areas of territory.

Kyle Orton, a fellow at the centre, said: “Far from battling terrorism they’re in effect aiding one proscribed terrorist organisation overcome another.
“The government needs to act now to prevent Britons falling into this trap. “If they’re already there and want to come back, comprehensive tests need to be put in place to prevent potentially dangerous individuals within our communities.”

The father of a British man who died fighting with the YPG against IS in March 2015 said he was “deeply hurt” by the think tank’s report.

Chris Scurfield, the father of Erik Scurfield, the first British man to be killed fighting against IS with the Kurds, said the report had upset families of British volunteer fighters. He said: “We are speaking with other bereaved parents whose children also lost their lives in Syria, fighting alongside coalition forces to defeat ISIS and save the lives of civilians.”