Britons who fight for Islamic State have picked a side and are enemies of the British state, David Cameron has told Tory activists in Birmingham.
The Prime Minister vowed the Government would do everything it could to stop people travelling into the war zone to fight alongside Islamic State, also known as Isil.
But he had a harsh message for those already there.
Mr Cameron said: “You have declared your allegiance. You are an enemy of the UK and you should expect to be treated as such.”
He added: “And to those who have had all the advantages of being brought up in Britain but who want to go and fight for Isil, let me say this: if you try and travel to Syria or Iraq we will use everything at our disposal to stop you.
“Taking away your passport, prosecuting, convicting, imprisoning you. Even if you are there already, we may even prevent you from coming back.”
Defending the UK’s role in the new Iraq war, he said: “The end of the Afghan mission does not mean the end of the threat - the threat is Islamist extremist terrorism and it has found a new hellish crucible with Isil in Iraq and Syria.
“These people, they are evil - pure and simple. They kill children, rape women, threaten non-believers with genocide, behead journalists and aid workers.
“Some people think we can opt of this.
“We can’t. As I speak, British servicemen and women are flying in the skies over Iraq. They saw action yesterday and there will be troops on the front line.
“But they will be Iraqis, Kurds, and Syrians fighting for the safe and democratic future that they deserve.
“We are acting in partnership with a range of countries including those from the region because let us be clear: there is no walk-on-by option.
“Unless we deal with Isil, they will deal with us, bringing terror and murder to our street. As always with this party, we will do whatever it takes to keep our country safe.”
At a fringe event at the Tory conference on Tuesday nightnight, Work and Pensions Secretary Iain Duncan Smith insisted the Cabinet, including Liberal Democrat members, unanimously believed IS would have to be dealt with in Syria.
Labour’s reluctance was behind the Government’s decision only to seek approval for air strikes on forces in Iraq, he added.
“The reality, I have to be honest with you, is that it is a Labour issue, it is an issue for the Labour Party. “We need to carry the Commons on these things and so the answer here is that Labour decided that frankly this was not a step they wanted to take, so it conditions what we are doing.”
“To be honest with you, there was absolute unity around the Cabinet table, including the Liberal Democrats as well, all basically saying the same thing - that the complete package is ultimately having to deal with Isil, not Isil in one place.”
Defence Secretary Michael Fallon last night confirmed that two Tornado GR4s from RAF Akrotiri in Cyprus were tasked to assist Kurdish troops who were under attack by IS.
They successfully destroyed a heavy weapons post and pick-up lorry with a mounted machine gun.
Meanwhile, the wife of British hostage Alan Henning issued a renewed plea for Islamic State to release her husband.
Mr Henning, a 47-year-old former taxi driver from Salford, was kidnapped last December in Syria and was featured in an IS video last month depicting the murder of fellow-captive David Haines.
His wife, Barbara Henning, said: “I ask Islamic State: please release him, we need him back home.”
She added: “Some say ‘wrong time, wrong place’. Alan was volunteering with his Muslim friends to help the people of Syria. He was in the right place doing the right thing.”
The extremists have released a third propaganda video appearing to feature the British photo-journalist John Cantlie.
The clip, which lasts for five and a half minutes, shows Mr Cantlie sitting at a desk dressed in the now-familiar orange outfit worn by other IS hostages.
The video is introduced with the title Lend Me Your Ears and Messages From The British Detainee John Cantlie before the Briton appears on screen.
Mr Cantlie, who looks calm and appears to be reciting a prepared script, describes himself as a ‘’long-term prisoner’’ and goes on to criticise US president Barack Obama’s strategy of attempting to defeat IS fighters using air strikes.