Hundreds of the Manchester Arena bombing survivors, along with relatives of the victims, have launched legal action against MI5, claiming it failed to take action that could have stopped the attack. More than 250 people have joined the group action against MI5 and have submitted their claim to the investigatory powers tribunal, which hears complaints against the intelligence services. It is believed to be the first time MI5 has been sued over its failure to stop a domestic terror attack. A statement on behalf of Hudgell Solicitors, Slater and Gordon, and Broudie Jackson Canter, the three lead firms representing the group, said: “Legal teams representing injured survivors of the Manchester Arena bombing in 2017 can confirm that they have collectively submitted a group claim on behalf of more than 250 clients to the investigatory powers tribunal (IPT). “As it is an ongoing legal matter, we are unable or provide any further details, or comment further, at this stage.” The security service’s director general, Ken McCallum, previously issued a public apology over the failure to stop the suicide bomber Salman Abedi, 22, whom MI5 had received intelligence about in the run-up to the atrocity. An inquiry into the attack, which left 22 people dead and hundreds injured, concluded that MI5 missed a “significant opportunity” to prevent the bombing. The inquiry’s chair, Sir John Saunders, said there was a “realistic possibility” investigators could have stopped the bombing if they had acted more decisively on two key pieces of intelligence, but it was “quite impossible” to say definitively whether any different action would have prevented the blast. Andrew Roussos, the father of eight-year-old Saffie Roussos, who was the youngest of those killed in the attack, previously said suing MI5 was the “only way to learn”. “Everybody learns by hitting them hard in the pocket, I am sorry to say,” he told Times Radio. “At 2017 we were at the highest alert and everybody was warned of an attack in this country, and MI5 – who, their sole job, they are well funded and well equipped – had 22 pieces of information about Salman Abedi. “So, if they would have learned lessons, they wouldn’t have allowed Abedi to walk into that arena. So, yes, MI5 have, for me, most of the blame.” Abedi detonated a homemade bomb in the foyer of Manchester Arena on 22 May 2017 as hundreds of people were leaving an Ariana Grande concert, in the deadliest terror attack in Britain since the 7 July 2005 bombings in London. He had packed the bomb with metal nuts and bolts that left many of the survivors, mostly children and young people, with serious injuries. The inquiry into the attack, which concluded last year, found that Abedi’s return from Libya four days before the blast would have been taken “extremely seriously” by MI5 had key pieces of intelligence been taken more seriously in the preceding months . It also found that the agency could have discovered Abedi’s homemade device, stored in a car in Manchester, if an investigation had begun earlier. Roussos said: “Salman Abedi should not have made it to that arena that night. There were too many missed opportunities.”