MI6 chief Sir John Sawers said the leaks from NSA whistleblower Edward Snowden "have been damaging and put operations at risk."
Al-Qaeda is "lapping up" the leaks and Britain's enemies are rubbing their hands with glee, the British intelligence chief added.
More top news
Newly released audio recording of Mohamed Emwazi, aka "Jihadi John", reveals his claims that he was threatened by MI5 five years ago.
"I really think that the focus of your outrage should be people who throw gay men off cliffs", said London Mayor, Boris Johnson.
Archaeologists have discovered eight mass graves holding more than 200 bodies between them hidden beneath a supermarket in Paris.