Eight people were killed two years ago when three men drove into pedestrians on the bridge before stabbing other people nearby.

In a new report, Judge Mark Lucraft QC said the system for granting extra security measures was “too rigid”.

Judge Lucraft said: “The national criteria for identifying sites which would receive proactive advice were apparently too rigid.”

He added that public authorities, such as councils, may require a legal duty imposed on them to review open and crowded spaces in order to minimise the risks associated with an attack.

The report also called on the government to look at criminalising “possession of the most serious material glorifying or encouraging terrorism”.

Judge Lucraft said that, under current law, it might be impossible for police or the intelligence services to act even when “the material is of the most offensive and shocking character”.

The chief coroner said this represented a significant gap in the law. The ringleader of the attack, Khuram Butt, had a large volume of extremist material on his phone but had not been charged with any crime.

“While there are offences of possessing a document likely to be useful to a person in committing an act of terrorism, and of disseminating terrorist publications, there is no offence of possessing terrorist or extremist propaganda material,” the judge said.