But the commissioners say their motives are "pure", and they simply want their crime-fighting tools to be brought into the 21st century.

Australian Federal Police Commissioner Tony Negus, NSW Police Commissioner Andrew Scipione and South Australian Police Commissioner Gary Burns have this morning given evidence to an inquiry into proposed laws that would force telecommunication companies to store phone and internet data for two years.

Under the proposed laws, so-called "metadata" – which includes times, locations and durations of phone and internet communication – could be accessed by authorities with a warrant.

The three say they agreed to appear at the inquiry in Sydney on behalf of Australia's police commissioners to stress the importance of changing telecommunications laws to make it easier for police to access telco information to investigate crimes.

Mr Negus said police did not seek access to Australians' emails, but strongly supported "maintaining existing [warrant] capability in the face of changing technology".

But he told the inquiry in Sydney that police would "ideally" prefer the information be held by telecommunication companies indefinitely, so it could be accessed by police at any time.

"The two-year proposal ... we could live with," he said. "It certainly wouldn't be ideal, but we could live with [it]."

The police chiefs said the nation's police forces were struggling with telecommunciations intercept laws written in 1979, which had been overtaken by rapid technological advances.

Mr Negus said police simply wanted to access information they could formerly demand with warrants; "maintaining existing capability in the face of changing technology".

Mr Scipione said: "Our motives in this are true and pure. We just want to keep Australia the safest nation on the planet."

The controversial data retention proposals have been outlined in a discussion paper circulated by the Attorney-General, Nicola Roxon.

The laws have come under fire from privacy and legal circles over fears that unreasonable amounts of data could be stored, and that there will be inadequate safeguards put in place to protect personal information.

At a hearing in Melbourne this month, the Labor senator John Faulkner raised questions about the lack of detail contained in the discussion paper.

"I have said before that there are no safeguards outlined," he said.

"In fact, the detail about the proposal itself is obviously very limited."

The police commissioners said they wanted to be involved in drafting new reforms, or even new legislation, arguing criminals were now able to operate outside the reach of telecommunication laws and law enforcement agencies.

Mr Scipione said, "increasingly we're trying to deal with crimes that are so new that we're learning on a daily basis ... we simply want to be able to hold our own".