Ministers have been urged to "toughen our terror laws" after it emerged only one in ten British jihadis have been prosecuted upon their return to the UK.
It is estimated that about 400 Britons have returned to the UK from the Middle East since 2012 after leaving to fight for terrorist groups such as Islamic State.
Home Office Minister Ben Wallace, in a Commons debate on new counter-terrorism and security proposals, revealed that of the 400, around 40 had been prosecuted for "direct action they've carried out in Syria".
Barrow and Furness MP John Woodcock, who had pressed for the figures, said the low prosecution rate "shows how urgently we need to toughen our terror laws".
Speaking in the debate, Mr Woodcock added: "So, only one tenth of people have been successfully prosecuted.
"That does not mean the others are innocent of terrorism charges, if they have been over to Iraq and Syria, if they have been aiding Daesh in whatever form and they are British citizens, they have been aiding enemies of the British state."
Mr Woodcock called on the Government to introduce a similar system to that in place in Australia, whereby certain areas are deemed illegal to travel to.
Home Secretary Sajid Javid said he would be "looking at just that", adding: "There's a bit more work to do on it, it's not as straightforward as it might sound."
Earlier in the debate, shadow home secretary Diane Abbott voiced concerns over threats to freedom of speech by a lack of clarity in the Counter-Terrorism and Border Security Bill.
Ms Abbott said: "On the question of expressing opinion, the Home Office said in its notes on the Bill that it is not making it an unlawful act to hold a private view in support of a terrorist organisation.
"The Home Office also says that operational experience has shown there is a gap around individuals who make statements expressing their own support for terrorist organisations but who stop short of expressly inviting others to do so.
"The Home Secretary will expect we will press this point in committee because we would say the gap between having a personal opinion and inciting other unlawful acts is not an anomaly, it is an important principle in protecting freedom of speech.
"We're in danger in this legislation of confusing bad thoughts with bad deeds, but we hope to clarify this issue as the Bill goes through the House."
Tory MP John Howell, who sits on the Commons justice committee, later warned ministers that they ran the risk of radicalising more people by extending prison sentences for terror offences.
The Henley MP said: "On my notes to this debate, I have written 'so they will be more radicalised, by spending more time in prison'.
"I think that that is a risk that we run with extending the prison sentences by ensuring that they are more susceptible to the influences that are going to effect that radicalisation process. What we need to do is to address that in total from the beginning."
Mr Javid said he was taking a "long, hard, forensic look" at powers available to the police, security services and the judiciary to ensure they have what they need.
He said the Bill would allow the police and MI5 to "disrupt threats earlier and to ensure that our laws reflect the modern use of the internet".