Spooks and security agencies must openly debate the public's concerns over surveillance following the Snowden revelations, former head of MI5 and current thriller writer Stella Rimington has said.
"It is not enough nowadays for intelligence services to say we have your best interests at heart," she told delegates at Microsoft's Future Decoded event in London.
Rimington praised the new head of GCHQ, Robert Hannigan, for "putting his head above the parapet" to discuss the eavesdropping agency's surveillance practices.
Last week Hannigan slammed US technology companies for improving the security of their products.
“However much they may dislike it, they have become the command and control networks of choice for terrorists and criminals, who find their services as transformational as the rest of us,” he wrote in the Financial Times.
"The balance between freedom and government responsibility to look after us is a delicate line," said Rimington.
"Today's leaders need to be prepared to engage in the debate," and must legitimately make the case for surveillance, rather than hiding, she said.
"Not everybody will agree, but [it is] important that that case is made."
She added: "It is a question of do you trust us, or do you trust Snowden or do you trust the Islamic State?" ®