This undated file combination image released by the Metropolitan Police shows Lee Rigby's killers Michael Adebolajo, left, and Michael Adebowale. British lawmakers say two Islamic extremists who murdered a soldier in a London street had been under scrutiny by the intelligence services, and one had expressed his intention of killing a soldier in an online exchange months before the attack. Parliament's Intelligence and Security Committee says that if British spies had known of Michael Adebowale's declaration, "there is a significant possibility" they could have prevented the murder. (AP Photo/Metropolitan Police, File)
LONDON — Britain's intelligence agencies were monitoring two al-Qaida-inspired extremists who killed a British soldier on a London street, but did not know about a key online exchange that could have alerted authorities to the impending attack, lawmakers said Tuesday.
Parliament's Intelligence and Security Committee said that if a U.S.-based Internet firm had told British spies about Michael Adebowale's online declaration that he wanted to kill a soldier, "there is a significant possibility" the May 2013 murder could have been prevented.
But the report concluded that spy agencies "were not in a position to prevent the murder" with the information they had at the time.
Adebowale's "explicit and emotive" exchange with an extremist overseas was only discovered after he and Michael Adebolajo killed Fusilier Lee Rigby in front of shocked bystanders on a busy street. After the slaying, Adebolajo was filmed ranting about British policy in Muslim lands while holding bloody knives.
The committee's 192-page report into the attack found delays and other failings by British intelligence agencies. But it leveled its strongest criticism at U.S.-based Internet companies such as Google, Twitter and Yahoo, which it accused of failing to report extremist content or comply with British requests to hand over information.
The report did not identify the company involved in Adebowale's online declaration, but British media identified it as Facebook.
Facebook said in a statement that it did not comment on individual cases but "we do not allow terrorist content on the site and take steps to prevent people from using our service for these purposes."
Responding to the report, Prime Minister David Cameron said Internet companies had a social and moral responsibility to avoid being used in terrorist plots.
He said that if companies "provide services in the U.K. they should be subject to U.K. law," and told lawmakers he had raised the issue with President Barack Obama.
Isabella Sankey of human rights group Liberty accused the committee of seeking "to blame the communications companies for not doing the (intelligence) agencies' work for them."
The report said that the two attackers had shown up on spy agencies' radar in seven different investigations, and in two of them Adebolajo had been labelled a "high priority."
The committee criticized Britain's foreign intelligence agency, MI6, for a four-month delay in opening an investigation into Adebolajo after he was arrested in Kenya in 2010 while attempting to travel to Somalia to join al-Shabaab militants.
The report also expressed concern about how long it took MI5 to request that Adebowale be put under "intrusive" surveillance. An application was submitted to the Home Office the day before the attack.
Rigby's uncle, Raymond Dutton said he accepted that the murder could not have been stopped. He said his nephew "was in the wrong place at the wrong time."
"If it hadn't been Lee, it would have been someone else," he said.