Government restrictions on terrorist suspects are now considered so ineffective ministers may be unwilling to use them any longer, the official counter-terrorism watchdog has warned.
David Anderson QC, the independent reviewer of counter-terrorism legislation, warned the system of Terrorism Prevention and Investigation Measures (TPims) could be in need of an overhaul barely two years after its introduction by the coalition.
Giving evidence to the parliamentary Joint Committee on Human Rights, Mr Anderson said only one new TPim had been imposed since 2012 and there were none currently in force.
While he said that it may in part reflect the number of prosecutions and deportations, he said ministers may be reluctant to take the "political risk" of using them after two high profile cases in which suspects absconded.
In one case the suspect fled after changing into a burkha while visiting a mosque while the other disappeared in a black cab after ripping off his electronic tag, leading one radical pressure group to claim "anyone who wants to escape from a Tpim can".
"That seems to me an extremely damaging perception and it may be part of the explanation for why no TPims have been made over the last year-and-a-half ," Mr Anderson told the committee.
"l can only imagine that the political risk of imposing one of these TPims if the person then subsequently escapes - whether dressed in a burkha or otherwise - could be quite large.
"Therefore one might instinctively look to other ways of neutralising the threat than a TPim.
"I think we may need to look again at whether they are actually fully effective to their job of preventing terrorist activity and containing the person who is subject to them."
TPims were first introduced in 2012, replacing the more restrictive control orders brought in under the former Labour government.
It followed a bitter coalition battle between Home Secretary Theresa May and Deputy Prime Minister Nick Clegg who insisted upon a less restrictive regime.
Restrictions available under TPims include overnight residence at a specified address, GPS tagging, reporting requirements and restrictions on travel, movement, association, communication, finances, work and study.