Twenty-two people - the youngest aged eight - died and more than 200 were injured when a man detonated a homemade bomb at Manchester Arena in northern England as parents arrived to collect children following the U.S. singer's show.

John Saunders, the chairman of a public inquiry into the tragedy, said he could not say for certain the bombing could have been stopped, but "there was a realistic possibility that actionable intelligence could have been obtained, which might have led to action preventing the attack".

He said the domestic MI5 spy agency, whose officers he questioned during private hearings, had failed to act swiftly enough. Saunders spoke after publication of his third and final report into the bombing, the deadliest in Britain since the 2005 London transport suicide attacks.

Ken McCallum, MI5's Director General, said he was "profoundly sorry" that his service had not prevented the attack.

"Gathering covert intelligence is difficult – but had we managed to seize the slim chance we had, those impacted might not have experienced such appalling loss and trauma," he said in a statement.

Saunders told a media conference there had been a "significant missed opportunity to take action that might have prevented the attack." He said he was unable to give details because of national security concerns, admitting this might leave victims' families wanting to know more.

'SO MANY FAILED IN THEIR DUTIES'

Richard Scorer, a lawyer for 11 bereaved families, said Saunders' report had exposed "unacceptable" failures.

"At the very least, a real possibility of preventing this attack was lost. This is a devastating conclusion for us," he said.

The bomber, 22-year-old Salman Abedi, had been known to the security agency since 2014, had visited an influential jailed militant in prison, and should have been referred to a de-radicalisation programme, Saunders said.

Abedi's younger brother Hashem was jailed for 55 years in 2020 for encouraging and helping him while a third, older brother, Ismail, was in July convicted in his absence of failing to attend the inquiry to give evidence, having fled Britain.

The brothers were born to Libyan parents who emigrated to Britain during the rule of Muammar Gaddafi,

Interior minister Suella Braverman said she would work with the agency and police to "do everything possible to prevent a repeat of this horrifying attack."

Saunders' previous two reports had also highlighted other shortcomings and mistakes made both in the security at the venue and in the response by the emergency services, saying one victim would probably have survived had it not been so flawed.

Some victims' relatives said they could never forgive those who had let their loved ones down.

"From top to bottom - MI5 to the associates of the attacker - we will always believe that you all played a part in the murder of our children," Caroline Curry, the mother of a teenage boy who died alongside his 17-year-old girlfriend.

"So many people being paid that night to protect our kids, and yet so many failed in their duties."