Social media giants like Facebook and Google will face new laws to compel them to help Australian security agencies get access to encrypted messages from suspected terrorists and other criminals.

Key points: George Brandis says laws will help with investigations into paedophile networks, organised crime

George Brandis says laws will help with investigations into paedophile networks, organised crime Security expert warns against "building weaknesses into the design of encryption"

Security expert warns against "building weaknesses into the design of encryption" Labor to carefully consider the details of the legislation

Prime Minister Malcolm Turnbull said the law had not kept up with technology, with encryption now affecting 90 per cent of domestic spy agency ASIO's priority cases.

The new laws will be similar to Britain's Investigatory Powers Act, which imposes an obligation on companies to cooperate with investigations.

Attorney-General George Brandis said encryption was potentially the "greatest degradation of intelligence and law enforcement capability" in a lifetime.

If the laws are passed and technology companies comply, they could help with investigations into paedophile networks, major organised crime or terrorism.

He said the Coalition's "very strong first preference" was for companies to volunteer their help, but the Government would still be able to force them to act where reasonable and necessary.

"Potentially, as the United Kingdom has done with its Investigatory Powers Act, as the New Zealanders did in 2013 with their equivalent legislation," he said.

"What this does is merely contemporise for the modern era what is a well-established legal principle and that is persons, including companies, can be subject to an obligation to assist law enforcement in solving crimes."

Senator Brandis said that would be on a warranted basis, as in the UK.

He said the UK's chief cryptographer had assured him the new approach was feasible.

Mr Turnbull said the move would bring the obligations on internet companies in line with those placed on telephone companies.

"We cannot allow the internet to be used as a place for terrorists and child molesters and people who peddle child pornography, and drug traffickers to hide in the dark," he said.

"The laws of mathematics are very commendable but the only laws that apply in Australia is the law of Australia."

Weakening system would affect everyone: Facebook

Facebook, which also owns WhatsApp, one of the world's most popular encrypted messaging apps, warned against being forced to weaken their systems.

The Silicon Valley tech giant provided data to police and intelligence officials 657 times last year.

"Weakening encrypted systems for [law enforcement] would mean weakening it for everyone," a spokesman said.

"We appreciate the important work law enforcement does and we understand their need to carry out investigations.

"That's why we already have a protocol in place to respond to requests where we can."

New data from the Government shows the amount of encrypted communications intercepted by ASIO has risen to more than 55 per cent in July this year, up from just 3 per cent in 2013.

More than 65 per cent of data being lawfully intercepted by the Australian Federal Police now also uses some form of encryption.

Last month, that saw it affect around 60 terrorism and organised crime operations.

Encryption has also featured in attack planning for incidents such as the 2015 Paris attacks.

The laws will also give the Australian Federal Police the ability to remotely monitor computer networks and devices.

Expert warns against 'building weaknesses' into encryption

Independent security researcher and consultant Troy Hunt said phone applications and messaging services were programmed to automatically encrypt communications and the procedure was so sophisticated even the tech giants themselves could not decode the messages on their own platforms.

"As soon as you start to build in weaknesses into the design of encryption, you put it at risk for everyone," he said.

Labor frontbencher Anthony Albanese said the Opposition would carefully consider the details of the legislation.

"We'll look at any legislation with the same approach we've had to all of this, which is a common sense approach that we must keep Australians safe," Mr Albanese told Channel Nine.

"Governments have that responsibility and we should have a bipartisan approach."

Mr Turnbull called for action on terrorists using encrypted messages at the G20 summit this month, and Senator Brandis has also raised the issue at a meeting with Australia's Five Eyes intelligence partners.

The legislation is set to be introduced to the Parliament before the end of the year.