A former head of Britain's domestic security agency has warned that cracking down on the use of online encryption could lead to more illicit hacking.
Lord Jonathan Evans, who was head of MI5 between 2007 and 2013, told the ABC there was a strong public interest in ensuring individuals and businesses continued to have access to important cyber security technology.
"My personal view is that we should not be undermining the strength of cryptography across the whole of the cyber market because I think the cost of doing that would be very considerable," Lord Evans said.
"I think if you don't have secure encryption, it makes it easier for the hackers.
"It means it's easier to get into financial services, into people's private emails, into their own messages when there isn't lawful authorisation."
The Turnbull Government is working on legislation designed to force tech companies to hand over encrypted messages to prevent terrorism and solve crimes.
It is thought that the planned legislation could draw on British laws introduced in 2016.
Before the UK legislation passed, Apple chief executive officer Tim Cook warned it could have "dire consequences" by providing a back door to devices where personal data and communications could be stolen.
Lord Evans was not commenting directly on the Turnbull Government's proposals, but said any politicians planning to tackle terrorists who used encryption methods needed to juggle the competing interests.
"On the one hand, there is a general consensus that with appropriate lawful authorisation, it's right that the government or government agencies can access the communications of those people who cause a threat," he said.
"On the other hand, there is also a very strong public interest in ensuring that we have cyber security so we can live our lives on the internet, so we can undertake our business activities on the internet."
Lord Evans made the comments before giving the keynote address at a lunch at Australia House in London organised by Business Events Sydney.
The former MI5 chief has spent most of his professional life fighting terrorism.
He worked as a senior intelligence official in Northern Ireland in 1990s, was in charge of British efforts to combat Al Qaeda after 9/11 before taking over as director-general of Britain's domestic intelligence agency.
He said tech companies have a responsibility to work with intelligence agencies.