British Isil fighters should be killed in Syria rather than be allowed to return to UK, a Government minister has said. Rory Stewart said converts who leave Britain to fight for the terror group are guilty of horrific acts and the only way of dealing with them is to kill them "in almost every case". His remarks come just days after the independent reviewer of terrorism legislation Max Hill QC said young people who travelled to Syria after being "brainwashed" should be allowed to come home and rejoin society. Mr Hill told the BBC that it was not worth losing a generation of young people who "naively" went to join Isil before attempting to come back to the UK. Asked by BBC Radio 5 Live's John Pienaar if they had "brought on themselves what they are about to get?", he said: "These are people who have essentially moved away from any kind of allegiance towards the British Government. A female sniper of the Syrian Democratic Forces Credit: AFP "They are absolutely dedicated, as members of the Islamic State, towards the creation of a caliphate, they believe in an extremely hateful doctrine which involves killing themselves, killing others and trying to use violence and brutality to create an eighth century, or seventh century, state. "So I'm afraid we have to be serious about the fact these people are a serious danger to us, and unfortunately the only way of dealing with them will be, in almost every case, to kill them." Around half of the estimated 850 Britons believed to have gone to join the extremists are now believed to be back in the UK. There are fears more will follow as the terror organisation loses territory in Iraq and Syria. Mr Stewart's comments come after the defence secretary Michael Fallon said earlier this month that anyone who chooses to leave the UK to fight for the Islamic State runs the risk of being killed. Mr Fallon said: “If you are a British national in Iraq or Syria and if you have chosen to fight for [Isis] – an illegal organisation that is preparing and inspiring terror attacks on our streets – then you have made yourself a legitimate target and you run the risk every hour of every day of being on the wrong end of an RAF or a United States missile.” FAQ | Islamic State Mr Hill, who called for former Isil fighters to be allowed to reintegrate back into the UK, was supported by Conservative MP Andrew Rosindell, who sits on the Commons foreign affairs committee. He said: "The presumption should be that all people who went to join IS should be dealt with by the criminal justice system unless there is a good reason why not. "IS is an utterly barbaric organisation still intent on carrying out terror attacks in Britain and everything possible must be done to stop its supporters being involved in such atrocities." But Mr Stewart said converts to the terror group believed in an "extremely hateful doctrine", saying fighters can expect to be killed given the threat they pose to British security. Hundreds of British citizens are known to have travelled to Syria to fight with Islamist groups during the course of the six-year conflict. Brett McGurk, a top US envoy for the coalition fighting Islamic State (IS), has said his mission is to ensure every foreign IS fighter in Syria dies in Syria. Seven foiled UK terror plots Mr Stewart was asked about claims made by Mr McGurk that foreign fighters do not make it back to their country of origin and die in Raqqa or wherever they are serving. Coalition forces are reported to have given a list of names and photos to Kurdish fighters on the ground so that they can identify and kill foreign fighters before they have the chance to escape as they are seen as a security threat. However this could allow room for some fighters, identify as less serious offenders, to be allowed to return home. Mr Stewart, a former diplomat, went on to say: "These are people who are executing people in the back of their heads, who have held women and children hostage, who are torturing and murdering trying by violence to impose their will. "Our response has to be, when somebody does that, I'm afraid, to deal with that." Mr Stewart also said British authorities had made it "very clear" that people should not be volunteering with militia groups to fight IS. "If you wish to serve your country and you wish to fight terrorism, then please apply to join the military or join the police or join our intelligence services, we'll train you, we'll work with you to do it in a legal and controlled fashion," he said. Mr Stewart confirmed it remained British policy to remove Syrian president Bashar Assad. "I don't think anyone should be in any doubt that the control that he has is brutal and ultimately fragile," he said. "The policy of the British Government is that Bashar al-Assad needs to step aside and we need transition to a new government, because so long as that man is in power it is going to be impossible to have a long-term, stable, sustainable future for Syria."