Australia's top cyber security adviser says people will be at risk without new laws to deal with encrypted communications.

Home Affairs Minister Peter Dutton has written to the chair of a parliamentary committee, Liberal MP Andrew Hastie, stressing the need to speed up a report into encryption access laws.

Mr Dutton and Prime Minister Scott Morrison want the laws passed in the coming fortnight, the last period of parliamentary sittings for the year.

But the committee is still scrutinising the laws and has planned a series of public hearings in the coming weeks.

National cyber coordinator Alastair MacGibbon, a former federal police officer, says up to 80 per cent of communication interceptions these days are encrypted, making it difficult for investigators to deal with criminals.

"That actually puts Australians at risk," he said.

He says encryption is useful, in terms of making banking and government transactions safe.

But it is also used by people who wish to cause harm such as child sex offenders and terrorists.

"The vast bulk of the law is actually codifying our conversation between industry, law enforcement, and security agencies to go after a very, very small part of the community who would do us harm," he said.

"It's not anti-encryption, it's anti-criminals using encryption."

The committee is now considering cutting short its inquiry to report in time for parliament to pass the laws.