The flight of young Britons to join Islamic State is not receiving enough attention from the state or Muslim communities, a former senior prosecutor has claimed.
Nazir Afzal, who led the CPS in north-west England from 2011 until earlier this year, said authorities should "resort to law" in cases where children are at risk of being taken to IS-controlled areas.
His comments come amid mounting fears that British sisters Khadija Dawood, 30, Sugra Dawood, 34, and Zohra Dawood, 33, and their nine children, aged between three and 15, have travelled to link up with IS - also known as Isis - in the country.
Mr Afzal told the Press Association: "The flight of young Muslims to Isis is not getting the attention from both the state and Muslim communities it requires.
"The state needs to clarify that Foreign Office 'advice not to travel' is more than advice.
"The international community has judged rightly that Iraq and Syria are unsafe areas. Therefore if a child is at risk of being taken there we should, if necessary resort to law to prevent them being taken."
Mr Afzal said this could include proceedings to make children wards of court being brought in appropriate cases.
A number of teenagers thought to be at risk of travelling to areas controlled by IS have been grounded by judges sitting in the Family Division of the High Court in recent months after social workers and police raised concerns.
Mr Afzal suggested court proceedings could also be used to stop those thought to be at risk of taking children from applying for travel documents.
"It's the basic principle in UK law that the 'welfare of the child is paramount' in the Children's Act and Universal declaration of the Rights of Child to which we are signatories," he said.
"That means what's in the best interests of the child, not their parents or carers."
He added: "For adults who are supposedly capable of making their own decisions then we have to be clear what we are saying.
"Having decided that Isis is hostile to British interests, it then shouldn't be a choice as to whether you travel. Do we really want a hostile force to receive new recruits or reinforcements?
"If the answer is no, then anyone at high risk of travelling shouldn't just be 'advised' not to go, but active steps should be taken including restricting their travel where appropriate.
"Freedom of movement is a right that can be qualified by a state where crime is being prevented."
Last year the Government outlined plans to prevent hundreds of young British Muslims from travelling to Iraq and Syria to fight with extremist militants by temporarily removing their passports.
Mr Afzal was also critical of Muslim leaders.
"The issue is only on the agenda when an individual crisis occurs," he said. "The propaganda that Isis is delivering needs a more robust and continuing response from these leaders in order to minimise its impact on families."
Police are "extremely concerned" about members of the missing Dawood family after receiving information that they may already be in Syria.
One of the sisters has made contact "and there is an indication that they may have already crossed the border into Syria", West Yorkshire Police said.
Their brother is believed to be fighting for IS in Syria and he reportedly persuaded his sisters over Skype to join him.
It has emerged that the same group tried to fly earlier this year.
The North East Counter Terrorism Unit confirmed that they had been stopped and made the subject of security checks earlier this year.
Speaking before the start of an international policing conference today, Metropolitan Police Commissioner Sir Bernard Hogan-Howe said: "There can never be any justification for a child being taken to a war zone."
He described the apparent situation of children being taken to Syria as "really difficult to understand".
He added: "Do you need to tell a mother not to take a child to a war zone? That seems really difficult. It must be that they are getting overwhelmed by some passion for the things they are attracted to in terms of what they believe is happening in Syria."
Sir Bernard said more research was needed to "understand what it is that is causing people to be attracted to something that most people think is barbaric".
He added: "We've got to understand more and come up with some structured way of intervening better."