MI5 would have had a better chance of stopping the Manchester bombing last year had it not made a catalogue of failings in the handling of suicide attacker Salman Abedi, a parliamentary committee has concluded.

The security agency failed to act on a number of occasions after he had come to its attention in the years before he detonated a nail bomb at a pop concert in 2017 that killed 22 people, according to Parliament’s intelligence and security Committee (ISC).

He was first on the MI5 radar in December 2010 and was briefly investigated by agents in 2014.

The ISC assessment said that Abedi visited an extremist prisoner on more than one occasion, but no action was taken afterwards by MI5 or police.

Abedi was permitted to travel with his father, a member of the Libyan Islamic Fighting Group, to Libya in 2011 to fight for the overthrow of the secular government of Muammar Gadaffi, despite the group having been banned as a terrorist organisation with links to al-Qaida in 2005. MI5 then decided not to place travel monitoring or restrictions on him, meaning he was allowed to return from Libya to Britain to commit the Manchester atrocity on Theresa May’s watch as home secretary.

ISC chairman Dominic Grieve said: “What we can say is that there were a number of failures in the handling of Salman Abedi’s case.”

Shadow home secretary Diane Abbott said MI5 failures raised “serious questions for the entire policing and security system.”

She added: “These questions include the proper identification, prioritisation and prevention of terrorists.

“But this government has undermined policing with cuts of 21,000 officers and community policing, the front-line ears and eyes on the ground in the fight against terror, has been hardest hit.”

Communist Party leader Robert Griffiths said the case highlighted far deeper issues around the accountability of our secret services and our government’s willingness to assist jihadists when it saw a use for them against foreign states.

“The fact that Abedi was able to do what he did is bound up with our government’s support for terrorists in Libya at that time and shows the urgent need for proper supervision of the intelligence services and a complete clearout of Establishment personnel at the top,” he told the Morning Star.