ASIO director-general Mike Burgess and AFP commissioner Reece Kershaw used a joint address at the National Press Club on Thursday urging greater cooperation from social media companies to allow access to encrypted communication as part of investigations.
While law enforcement agencies can request warrants to intercept encrypted messages, Mr Burgess said the communication cannot be read without the assistance of the tech companies.
"I'm not asking for new laws, I'm not asking for new powers, I'm not asking for more resources, I'm not asking the government to do anything," he said.
"I'm asking for the tech companies to do more ... without their help, in very limited and strictly controlled circumstances, encryption is unaccountable."
The ASIO head confirmed the spy agency had investigated an Australian communicating online with Islamic State supporters, with fears the supporters were encouraging them to commit a terrorist attack.
Mr Burgess said while investigations confirmed the communication took place, the lack of access to the encrypted messages had led to significant risks.
"If this individual was planning a terrorist attack, a quick and targeted access to communications could have been the difference between life and death," he said.
"I'm calling on big tech to establish lawful access solutions that can be applied in very tightly controlled and targeted situations, not to create back doors or systemic weaknesses that break the internet."
Issues involving end-to-end encryption had led to ASIO being "as busy as we have ever been" in the 75-year history of the organisation.
Mr Kershaw also reiterated the calls to social media companies on encryption, saying they had a responsibility to keep children safe online.
He said law enforcement capabilities were being undermined by the tech companies.
"We recognise the role that technologies like end-to-end encryption play in protecting personal data, privilege and cyber security," he said.
"But there is no absolute right to privacy. People have the right to privacy just like they have the right not to be harmed."
Mr Burgess indicated if the social media companies did not come to the table on encryption, a "conversation" with the government would be needed on possible new laws further compelling the platforms.
However, Mr Kershaw remained optimistic a middle ground could be reached.
AFP Commissioner Mr Kershaw says social media companies are failing to keep people safe online. (Lukas Coch/AAP PHOTOS)
"While end-to-end encryption provides solace to law-abiding individuals, it can also provide criminals with an in and invisibility cloak," he said.
"My door is open to all relevant tech CEOs and chairmen, including Elon Musk and Mark Zuckerberg. I know we can find common ground because, put simply, tech is supposed to make our lives easier and safer and not the opposite."
Communications Minister Michelle Rowland said the government was working with regulators and authorities in other countries to tackle the issue of encrypted platforms being used for extremism.
"National security agencies are deeply concerned about having the appropriate tools to do their jobs in order to keep Australians safe," she told ABC radio.
"These are smart people who are working with agencies and with their counterparts around the world, to be able to do what is necessary ... to identify where there are harms emerging and bring people to justice."