Newly imposed airport security measures are "unavoidable", the head of the parliamentary committee which oversees the work of Britain's intelligence agencies has said.
Sir Malcolm Rifkind, the chairman of the Intelligence and Security Committee, said jihadi extremists were deploying "devilish technical skill" to create ever more sophisticated devices to evade existing security measures.
Writing in The Sunday Telegraph, he warned of the dangers of "complacency" among the public in the face of the failure of the terrorists to mount any successful mass casualty attack in the UK since the 7/7 bombings in London in 2005.
His warning came as Abu Bakr al-Baghdadi, the shadowy leader of the Islamic State - formerly Isis - appeared in public before his followers to lead prayers at the Great Mosque in Mosul in northern Iraq where the extremist group has made sweeping gains.
The latest security measures imposed last week followed intelligence warnings that al Qaeda's chief bomb maker, Ibrahim Hassan al-Asiri, who is thought to be based in Yemen, had linked up with jihadists in Syria to pass on his skills.
Sir Malcolm, who disclosed that he had been briefed in advance about the measures, said that he had been left in no doubt that they were necessary.
"I have received fuller information than it has been possible to publish in the newspapers. I have no doubt, from what I have learnt, that these new steps are not bureaucratic nor an overreaction . Sadly, they are unavoidable," he wrote.
However, he said that he had encountered a level of complacency among some elements of the public which he found "seriously disturbing".
"It is simply foolish to believe that the threat is either minimal or now behind us. We have, indeed, been fortunate but, sadly, this has not been because the terrorists have, since 2005, given up trying to do us harm," he wrote.
"As Andrew Parker, the head of MI5, has made clear, each year there have been serious plots which if they had not been identified and disrupted would have led to the deaths and mutilation of many British citizens.
"The police and the security services have been very successful but we must not underestimate the devilish technical skill of those terrorists who design ever more sophisticated means of concealing explosives in mobile devices, in clothing and in otherwise innocent objects. They have been hard at work over the last year."