The head of Britain's security services has told a parliamentary committee that the revelations of whistleblower Edward Snowden will have the country's enemies rubbing their hands with glee.
Britain's three intelligence chiefs were grilled at a public hearing on Thursday.
In an unprecedented televised appearance, the heads of the domestic and foreign intelligence agencies, MI5 and MI6, as well as the Government Communications Headquarters (GCHQ) were asked about the impact of the Snowden revelations, the ABC reports.
The security chiefs said their adversaries were rubbing their hands with glee and that communications picked up from terrorist groups suggested they were changing the way they operated in light of information about the workings of the intelligence agencies.
There has been pressure on the agencies to be more transparent in the face of public disquiet in the wake of the Snowden revelations.
MI6 head John Sawers, said the Snowden leaks have put operations at risk. "It is clear that our adversaries are rubbing their hands with glee - Al Qaeda is lapping it up."
Sir Iain Lobban, the head of GCHQ, told the committee told that secret did not mean unaccountable.
He said terrorist groups in the Middle East are directly discussing certain elements of the leaks.
"We've seen terrorist groups in the Middle East, in Afghanistan and elsewhere in south Asia discussing the revelations in specific terms, in terms of the communications packages that they use, the communication packages that they wish to move to."