Terror suspects should not be granted police bail unless the decision is signed off by a prosecutor, senior legal figures have said.
It follows revelations about lapses that allowed Abu Rumaysah to flee the UK to join Islamic State despite being on authorities' radar.
Former director of public prosecutions Lord Macdonald and Nazir Afzal, who was chief crown prosecutor in north-west England from 2011 until last year, told the Press Association the CPS should be required to approve pre-charge bail in terrorism cases.
Rumaysah - born a Hindu called Siddhartha Dhar - was able to leave the country in 2014 despite being arrested six times.
He was held in September 2014 - when he was 31 - as part of an investigation into alleged support of the banned extremist group al-Muhajiroun.
He left Britain with his family the day after being released on bail, travelling to Paris and then Syria.
The episode has come under the spotlight following unconfirmed claims that Rumaysah was a masked militant at the centre of a gruesome film released last week showing the murder of five men accused by IS of spying for the UK.
Lord Macdonald said: "Given the sensitivity of these cases, and their obvious national security implications, any consideration of bail requires special care.
"The Siddharta Dhar case shows that It is not sufficient or safe for the police to decide this question for themselves.
"We urgently need a new rule that no police bail may be granted in terrorism cases without the explicit agreement of a specialist prosecutor from the CPS Counter Terrorism Division."
Mr Afzal said there is a "strong case" for prosecutors to have the final say.
"Fundamentally bail pre-charge has been a matter for the police with prosecutors often expressing a view which does not bind the police," he said.
"In serious cases such as terrorist allegations there is a strong case for requiring the police to not only consult with prosecutors but for the final decision to be made by prosecutors acting in the public interest."
He said that "the two most serious crimes are terrorism and murder" and "suspects in both should of course be given bail if there isn't enough evidence to charge but the prosecutor should always be consulted and they should have the final say".
A CPS spokesman said: "We work very closely with our police colleagues on all terrorism cases including pre-arrest.
"However any decision on bail conditions before a charging decision has been made is a matter for the police."
Following his release on September 26 2014, Rumaysah was given a week to voluntarily surrender his travel documents, which was a condition of his bail.
Earlier this week it emerged that a letter from police reminding him of the need to hand over the passport by October 3 was not sent until more than a month later on November 7.
Anti-extremist group Hope not Hate has claimed that five other suspected extremists who were either on bail or subject to travel restrictions have left Britain in the past 18 months.