A former Supreme Court judge has been named as Australia’s new national security monitor, tasked with reviewing a range of contentious policies.

Former New South Wales Supreme Court judge Roger Gyles has taken on the role of Independent National Security Legislation Monitor.

Mr Gyles has work piled up already, following the passage of two major bills to strengthen the powers of Australian spy agencies and crack down on Australians travelling overseas.

The Federal Government scrapped the watchdog position at the same time as it passed the bills, but has now re-appointed a monitor to look into the national security changes.

Mr Gyles is expected to look into whether recent changes will challenge journalists' ability to report on secret intelligence operations, for which jail terms now exist.

He will also have an important role reviewing new laws that force telephone and internet companies to retain customers' data, when the Government tries to pass them next year.

Mr Gyles said balancing national security needs with civil liberties is a daunting task.

“It involves going into a field, an important field and understanding it, under pressure of time but not so to jump the gun if you know what I mean,” he told the ABC.

He said the job of reviewing new powers given to the nation's security agencies will “be done in bite-sized chunks”.

“There obviously couldn't be a time element to that,” Mr Gyles said.

Mr Gyles has reportedly started the INSLM role immediately - on an acting basis until he is officially approved – in order to get stuck into the legislation for the Government’s next counter-terrorism package.

“It is important Mr Gyles consider this legislation as soon as possible. He will therefore commence as the INSLM immediately,” the Government said in a statement.

The Government believes Mr Gyles' previous experience will “equip him well for the important task of monitoring complex national security legislation”