Robert Hannigan, director general of the UK's eavesdropping agency General Communications Head Quarters (GCHQ), US and UK's intelligence agencies must develop a new relationship with tech companies, which had been at odds with them over encryption.
In a speech to the Massachusetts Institute of Technology, Hannigan called for dialogue in a less ''highly charged atmosphere''. He added that UK prime minister David Cameron would initiate a process in the next few months that ''can shed some really useful light. And, for my part, my promise today is to engage in that process with the tech industry openly, respectfully and in good faith''.
In 2014 Hannigan said websites were becoming ''the command and control centres of choice'' for terrorists and criminals. Intelligence agencies in both the UK and the US had been looking to force tech companies to provide a key or backdoor into their encrypted services, which, according to them was necessary to combat terrorism, international criminal gangs and paedophiles.
The issue had been highlighted by a row between the FBI and Apple. The bureau had been trying to force the company to create software for unlocking an iPhone that belonged to a gunman in a mass shooting in San Bernardino in December.
Security services are increasingly concerned over high levels of encryption on smartphone apps.
Hannigan said finding ''pragmatic answers, developed in an atmosphere which is less heated, must be in everyone's interests''.
''Of course some people will find new places to hide unlawful activities, and new channels of communication, but our agencies were created to tackle those hiding places,'' he said.
''What we need to avoid is effort diverted on all sides in tension between governments and the world's major providers.
''Instead we should apply our collective goodwill and technical brilliance to meeting the hardest threats to society.''