At least one in four of the estimated 2,000 foreigners fighting for ISIS in Syria and Iraq is British, and half of those are already back in the UK.
Serious questions have been raised as to whether enough is being done to stem the flow of fighters after the Government revealed it has only seized 23 passports this year to prevent them travelling to the war zone.
The Government says there are around 500 British among the fighters while a further 250 are thought to have already returned to the UK where the police and security services are attempting to watch them.
That means there are now almost three times as many British Muslims fighting for Islamic State than there are serving in the UK military.
According to the Ministry of Defence, there are around 600 British Muslims currently serving in the Armed Forces, just 0.4 per cent of total personnel.
Irish police also believe that 30 jihadists are using the country as a base while travelling to and from Syria and Iraq.
The murder of James Foley apparently by ‘John’ – one of a gang of British jihadis known as ‘The Beatles’ – has raised fears the killing fields of Syria and Iraq are dominated by extremist Britons.