More than 300 people affected by the Manchester Arena bombing cannot continue their legal action against MI5, judges have ruled.

Survivors and bereaved family members claimed their human rights had been violated by the failure of security services to take “appropriate measures” to prevent the May 2017 attack.

But Investigatory Powers Tribunal (IPT) judges Lord Justice Singh and Mrs Justice Farbey ruled their case had been brought too late and could not proceed.

Three law firms representing the claimants – Hudgell Solicitors, Slater & Gordon and Broudie Jackson Canter – described the judges’ decision as “extremely disappointing for our clients”.

Lawyers for the claimants added: “We are disappointed that time is one of the reasons now being used against them to prevent their claims from proceeding.

“Seven years have now passed since the atrocity in May 2017 – six years of the seven-year delay was caused by MI5.”

Twenty-two people were killed and hundreds injured when a suicide bomber detonated his device at the end of an Ariana Grande concert.

In March 2023, MI5 Director General Ken McCallum said he was “deeply saddened” that the security services had been unable to prevent the attack.

His comments followed a public inquiry which concluded that MI5 had missed a significant chance to take action that might have stopped the bombing.

Two pieces of information about the suicide bomber Salman Abedi had been assessed by the security service as not related to terrorism.

IPTs allow anyone who believes they have been the victim of unlawful action by a public agency using undercover investigative techniques to seek redress.

While dismissing the claim by the survivors and the bereaved, Lord Justice Singh said: “We are aware of the horrific impact of the atrocity on the claimants and their families.

“Any reasonable person would have sympathy for them.

“The grief and trauma they have suffered, especially where young children were killed, is almost unimaginable.

“Nevertheless, we have come to the conclusion that in all the circumstances it would not be reasonable to allow the claims to proceed.”

Lord Justice Singh said that while the panel could “readily understand” why the legal claims had not been raised until after the public inquiry’s final report, “proper expedition” had then been required.

He continued: “We are mindful of the other issues that need to be investigated and arrangements that need to be put in place, but in our view the filing of the proceedings was not given the priority that, objectively assessed, it should have been.”

The judge also pointed out that if the claims had been allowed to proceed, MI5 would have had to “divert time and resources to defending these procedures rather than their core responsibilities” to prevent future attacks.

Pete Weatherby KC, who represented the claimants at an earlier IPT hearing, described their legal action as the “next step” towards redress for them.

After the judges’ ruling, the plaintiffs’ lawyers said their clients had been forced to “endure continued delays” and noted that they “have done so with great patience and understanding in the hope that by allowing all legal processes to be fully explored, transparency and justice would be achieved.” .

The victims’ legal representatives said it should be clear that the IPT decision “definitely does not exonerate MI5”.

They added: “It was failures by MI5 and several other parties that led up to and on the evening of 22 May 2017 and together we continue to support our clients in their fight for full accountability and justice.”