Isis fighters returning to Britain could face treason trial, says Philip Hammond

500 UK citizens believed to be fighting for Isis

Philip Hammond said that ministers are considering the surprise move in response to hundreds of young Britons joining Isis (AFP)

British extremists who fight alongside Isis forces could be prosecuted for treason after they return to this country, the Foreign Secretary has told MPs.

Philip Hammond said that ministers are considering the surprise move in response to hundreds of young Britons joining Isis.

The offence of high treason carried the death penalty until 1998 and today has a maximum sentence of life imprisonment. No prosecutions for treason have been mounted since the aftermath of the Second World War.

In a Commons debate, the Tory MP Philip Hollobone called for UK citizens fighting for Isis to be prosecuted under the ancient charge.

He said: “Aiding and abetting enemies of Her Majesty is one of the greatest offences a British citizen can commit.”

Mr Hammond told him that ministers had already discussed the issue.

“There are a number of offences under English law with which returning foreign fighters can be charged. We have had a discussion about the allegiance question,” he said.

“We've seen situations of people declaring that they have sworn personal allegiance to the so-called Islamic State and that does raise questions about their loyalty and allegiance to this country and raises questions about whether offences of treason could have been committed.”

Some 500 UK citizens are thought to be among 1,500 foreigners fighting for Isis, while another 250 have already returned to Britain.

Meanwhile the Defence Secretary Michael Fallon announced that Britain is to redeploy its fleet of armed Reaper drones to Iraq to launch attacks against Isis in a significant escalation of the UK’s military effort. Nine Air Force Reaper drones, currently based in Kandahar, Afghanistan, and operated from RAF Waddington in Lincolnshire, will be shipped to the Middle East for use against Isis in the coming weeks.