The Government is considering introducing a new law to tackle terrorist propaganda in the wake of the 2017 London Bridge terror attack.
Chief Coroner Mark Lucraft QC identified a potential gap in legislation following inquests into the deaths of the eight people killed in the June 3 atrocity and their attackers.
Ringleader Khuram Butt, 27, had looked at extremist material online, including propaganda from the so-called Islamic State, violent images and sermons from extremist preachers.
The coroner said current legislation means it may be impossible for police or MI5 to act against fanatics even when “the material is of the most offensive and shocking character”.
And he suggested a new law could be introduced to tackle possession of the “most serious material glorifying or encouraging terrorism,” in a preventing future deaths report.
Responding on Tuesday, Home Secretary Priti Patel said: “The Government accepts this recommendation and is currently considering the necessity for a further offence of possessing the most serious extremist material which glorifies or encourages terrorism.”
Mr Lucraft suggested extremist material could be criminalised in the same way as the most offensive pornography.
Ms Patel said talks are ongoing between the Home Office and counter-terrorism police “as to whether there is a gap in the current legislation”.
“Our operational partners must have the tools and powers they require to tackle terrorism,” she said.
“The Government notes the Chief Coroner’s comments regarding the evidence at the inquests, the existence of the offence for a person in possession of a prohibited image of a child, and the perception that the lack of a comparative counter-terrorism offence may sometimes prevent counter terrorism policing from taking disruptive action.”
Eight people were killed and 48 others seriously injured when terrorists used a hired van to plough into pedestrians on London Bridge before attacking people at random around Borough Market on June 3 2017.
Butt, Rachid Redouane, 30, and Youssef Zaghba, 22, were lawfully killed after they were shot dead by armed police, an inquest jury found.
A separate inquest concluded that Xavier Thomas, 45, Chrissy Archibald, 30, Sara Zelenak, 21, James McMullan, 32, Kirsty Boden, 28, Alexandre Pigeard, 26, Sebastien Belanger, 36, and Ignacio Echeverria, 39, were unlawfully killed.
The coroner identified 18 “matters for concern” in a report published in November and told those responsible to address the issues.
But Patrick Maguire, an injury lawyer from Slater and Gordon, which represents the family of Mr Thomas and some of the surviving victims, said the recommendations came too late for those maimed and killed.
“The coroner’s report, and subsequent responses, reinforce my clients’ view there were a litany of unforgivable mistakes and missed opportunities by authorities which contributed to the death toll,” he said.
“It is troubling that many of the common sense improvements in authorities’ systems, procedures and protocols had to follow such a devastating loss of life.
“My clients hope these undertakings and commitments to improve are implemented faithfully and quickly.”
The inquest heard that police and MI5 did not recognise the threat posed by Butt, despite his association with Islamic State fanatic Anjem Choudary and an appearance in the documentary The Jihadi Next Door.
He was a subject of interest in an active MI5 investigation at the time of the attack.
But the probe was twice suspended due to pressure on resources and the authorities did not pass on tip-offs about his extremism, including one from a family member.
MI5 accepted, in its response to Mr Lucraft’s report, that the suspension of priority investigations was a “matter of legitimate concern” but insisted the decisions in Butt’s case “were sound”.
The security service said it had “reviewed and refined” its processes since 2017 but rejected the coroner’s suggestion that investigations could be scaled back rather than halted at times of high demand.
MI5 said: “In light of the flexibility within the suspension process and open investigations, the security service concludes that a new category of scaled back investigation is not required at this point and would not achieve the important aim of properly diverting specialist resource to those investigations deemed to be of the highest priority at the time in order to minimise the risk from attack plans judged to be imminent or which are deemed on the information available to pose the greatest threat to the public.”
The coroner also said action should be taken to reduce the risk of rented vehicles being used in terror attacks, which could include automated checking of rentals against lists of SOIs.
But trade body the British Vehicle Rental and Leasing Association (BVRLA), said the cost of real-time reporting needs to be considered, while the Government said there were “considerable challenges” to implementing such a scheme.
Jennifer Buchanan, a solicitor at law firm Field Fisher representing the family of Ms Archibald, who was killed when she was hit by the rented van, said: “It is encouraging that the BVRLA is taking steps to reinforce a culture of awareness among its members.
“We are concerned, however, that cost has been raised as a possible deterrent to implementing a formal system and also that there is not active consideration to introduce legislation to enforce real-time reporting.
“We hope this does not delay the introduction of vital measures to deter terrorists from being able to use vehicles as weapons which must be a priority.”
But Patrick Maguire, an injury lawyer from Slater and Gordon, which represents some of the victims, said the recommendations came too late for those injured and killed.
“The coroner’s report, and subsequent responses, reinforce my clients’ view there were a litany of unforgivable mistakes and missed opportunities by authorities which contributed to the death toll,” he said.
“It is troubling that many of common sense improvements in authorities’ systems, procedures and protocols had to follow such a devastating loss of life.
“My clients hope these undertakings and commitments to improve are implemented faithfully and quickly.”