The director of GCHQ has said it is time for a new relationship between US and British intelligence agencies and tech companies, which have been at odds over encryption.

In a speech to the Massachusetts Institute of Technology, Robert Hannigan called for dialogue in a less “highly charged atmosphere” and disclosed that David Cameron would set out 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 have been trying to force tech companies to provide a key or backdoor into their encrypted services, which they say is necessary to combat terrorism, international criminal gangs and paedophiles.

The issue has been highlighted by a standoff between the FBI and Apple. The bureau has been trying to force the company to create software to unlock an iPhone belonging to a gunman in a mass shooting in San Bernardino in December.

Hannigan, in only his second public comments, said he was not in favour of banning encryption. “Nor am I asking for mandatory backdoors. I am puzzled by the caricatures in the current debate, where almost every attempt to tackle the misuse of encryption by criminals and terrorists is seen as a ‘backdoor’. It is an overused metaphor, or at least mis-applied in many cases, and I think it illustrates the confusion of the ethical debate in what is a highly charged and technically complex area,” he said.

He told the audience it was a moral issue. “Defining what is reasonable and practical, of course, immediately engages proportionality. Does providing the data in clear endanger the security of others’ data? The unwelcome answer which dissatisfies advocates at both ends of the spectrum is: it depends.”

A bill is going through the UK parliament. It makes no concessions to the debate begun by the disclosures of the whistleblower Edward Snowden n 2013 other than to acknowledge powers used in the past and kept hidden from the public.

The UK approach contrasts with that of the US, where Congress last year passed the Freedom Act banning bulk data phone collection.

Hannigan said the investigatory powers bill did not give the UK intelligence agencies new powers but put in one place powers that had been spread across numerous statutes.