Updated 4.53pm

TWO ISLAMIC EXTREMISTS who murdered Fusilier Lee Rigby in a London street had been under scrutiny by intelligence services, a report has found, and one had expressed his intention of killing a soldier in an online exchange months before the attack.

The BBC has learned that the previously unnamed company ‘on whose system the exchange took place’ is Facebook.

The Silicon Valley firm has been accused of providing a safe haven for terrorists.

On the platform, Michael Adebowale said he wanted to kill a soldier and discussed plans to do so in the “most graphic and emotive manner”.

The UK’s Intelligence and Security Committee said Facebook believes it not does not have an obligation to identify conversations such as these.

The ICS says that if British spies had known of the declaration, “there is a significant possibility” they could have prevented the murder.

But the online exchange was only discovered after Adebowale and Michael Adebolajo killed Fusilier Rigby in May 2013.

The lawmakers concluded in the report published today that spy agencies had made mistakes, but that with the knowledge they had at the time they “were not in a position to prevent the murder of Fusilier Rigby”.

The two men, Adebowal and Michael Adebolajo, had appeared in seven different investigations by MI5.

A statement from the committee read:

There were errors in these operations, where processes were not followed, decisions not recorded, or delays encountered.

“However we do not consider that any of these errors, taken individually, were significant enough to have made a difference.”

While Adebolajo had been considered ‘high priority’ for MI5 investigations, “Adebowale was never more than a low level [subject of interest] and the agencies took appropriate action based on the rigorous threshold set down in law”.

However, if authorities had uncovered before that attack a conversation about killing a solider between Adebowale  and an individual overseas, ‘he would have become a top priority’.

US companies

The statement also notes that major US companies consulted during the investigation did not actively monitor and review suspicious content, and instead rely on user reports:

What is clear is that the one party which could have made a difference was the company on whose system the exchange took place. However, this company does not regard themselves as under any obligation to ensure that they identify such threats, or to report them to the authorities. We find this unacceptable: however unintentionally, they are providing a safe haven for terrorists.

They also did not feel compelled to comply with UK warrants, although new legislation has been brought in to amend this.

The chair of the report, MP Sir Malcom Rifkind, siad Rigby’s death “was first and foremost a tragedy for his family and friends”.

Our thoughts are with them today.

Additional reporting by Nicky Ryan and Sinéad O’Carroll