The suspension of priority MI5 investigations into the ringleader of the London Bridge attacks before the atrocity is a matter of “legitimate public concern”, the chief coroner for England and Wales has said.

In his Prevention of Future Deaths report, published on Friday, Mark Lucraft QC also suggested that further measures should be introduced to reduce the risk of rental vehicles being used in terrorist attacks.

Eight people were killed when three terrorists led by Khuram Butt, 27, drove a van into pedestrians on London Bridge and then began stabbing people in a 10-minute rampage on 3 June 2017.

MI5 had been been investigating Butt since 2015 over concerns he wanted to stage an attack. But the investigation was suspended twice, in 2016 and again from 21 March to 4 May 2017, weeks before the attacks.

The three attackers (left to right): Khuram Butt, Rachid Redouane and Youssef Zaghba. Photograph: Metropolitan police/PA

During the inquests, which concluded on 28 June after more than seven weeks of harrowing evidence, lawyers for the victims argued that valuable intelligence could have been lost as a result of the suspensions.

Lucraft’s report raises a number of other concerns about the actions of the security services before the attacks, as well as the response by emergency services on the night.

The families of the bereaved have accused MI5 of missing “opportunities galore” to stop the attack. Among the failings was a two-month delay in translating a request from Italian authorities for information about another of the attackers, Youssef Zaghba, 22. Additionally, material recovered from Butt’s phone and laptop during an October 2016 raid included Isis propaganda about martyrdom and suicide missions but the inquest heard no criminal charges resulted.

The families also criticised the response of the London Ambulance Service, whose staff did not enter the area where most of the victims lay dying until hours after the attack because it was designated a “hot zone”. Police officers were left to treat the wounded with the the help of members of the public, not knowing that ambulances were parked nearby on Borough High Street.

The chief coroner’s recommendations included:

Fresh laws on possessing the most serious material that glorifies or encourages terrorism.

Improving communications and co-working between MI5 and counter-terrorism police officers working on the same investigation.

Improving facilities for translating communications received from foreign security and intelligence services.

Increasing flexibility of the emergency response to marauding terrorist attacks.

Improving communications between the Met police and the London Ambulance Service.

Enhancing the first aid capabilities and equipment of either police officers generally or certain categories of officers.

He also suggested there were doubts about the “potential lone actor” tool twice used by MI5 to assess Butt’s risk. In September 2015, he was assessed as being of “medium risk”, and in May 2017 the assessment was “unresolved risk”.

On the suspension of investigations, Lucraft said: “Although MI5 must be able to prioritise and divert resources at times of greatest demand, the suspension of priority investigations is a matter of legitimate public concern. Accordingly, the systems for suspending such investigations (including the criteria for suspension, recording of suspension decisions and systems for rebuilding intelligence after suspensions) should be specifically considered in the continuing work of review and improvement.”

In relation to the risk of rental vehicles being used in terrorist attacks, the chief coroner said possible measures included introducing a scheme for real-time reporting of rentals and automated checking of the results against lists of subjects of interest.

At the conclusion of the inquest in June, Lucraft said he was “not persuaded” that the authorities had missed clues that could have helped thwart the atrocity, although the families voiced their disagreement. But he did criticise the failure to erect protective barriers on the bridge to thwart a vehicle attack three months after an attack on Westminster Bridge.

In Friday’s report, he highlighted the need for greater awareness around protective security, including the introduction of legal obligations, if necessary.

Helen Boniface, a senior associate at Hogan Lovells, who represented six families in the inquest, said: “Given the real risk of future deaths, we hope that the government, police, ambulance service and all other organisations named will now respond fully and ultimately implement effective measures in a timely fashion to address all issues that have been identified.”

Those killed by Butt, Zaghba and Rachid Redouane, 30, were Chrissy Archibald, 30, from Canada; Sébastien Bélanger, 36, from France; Kirsty Boden, 28, from Australia; Ignacio Echeverría, 39, from Spain; James McMullan, 32, from Brent, north-west London; Alexandre Pigeard, 26, a French national; Xavier Thomas, 45, a French national; and Sara Zelenak, 21, an Australian national.