Canberra lawyer Mr Collaery is appealing a decision in the ACT Supreme Court on Monday that would see large portions of his upcoming criminal trial heard in secret.

It's likely the appeal, listed for two days, will also be held behind closed doors.

The lawyer is accused of conspiring with his client, former spy Witness K, to reveal an Australian bugging operation on Timor-Leste, to which he has pleaded not guilty.

But before the trial, the attorney-general at the time, Christian Porter, made use of his powers under national security laws to intervene in the case and apply for secrecy orders. The government says these orders are necessary to protect Australia's national security interests.

The laws invoked by the government demand the court give "greatest weight" to the attorney-general's views about the national security implications of any given case.

Mr Porter has since stepped aside as attorney-general, though his successor, Michaelia Cash, has given no indication she intends to change course.

Human Rights Law Centre senior lawyer Kieran Pender said the attorney-general's use of secrecy in the case was "entirely undemocratic".

"It enables the government to concede in closed court that Australia spied on Timor-Leste while continuing to refuse to admit this publicly," he said.

"The NSI Act should be reformed to better safeguard the principles of openness and transparency that are at the heart of our judicial system.

"What our government did in Timor-Leste was wrong and unlawful under international law. The right thing to do would be to apologise to the Timorese people.

"Instead, the Morrison government is refusing to admit these misdeeds and prosecuting those who spoke up."

Mr Pender said there was no public interest in prosecuting either Mr Collaery or Witness K, who did the "right thing by exposing wrongdoing".

He called on the Commonwealth Director of Public Prosecutions to use her power to discontinue the prosecution.

The senior lawyer also said Australian whistleblowers were suffering at a "profound democratic cost" and they should be protected, not prosecuted.

He called on the federal government to overhaul whistleblower protection laws.

"A transparent Australia, where people speak up about wrongdoing, is a better Australia," Mr Pender said.

"The PID Act should be urgently overhauled to empower everyday Australians to feel safe and supported when they do the right thing and call out wrongdoing."

Mr Collaery and Witness K are accused of conspiring to breach intelligence laws which makes criminal the revealing of information of any kind about ASIS.

Witness K has indicated he will plead guilty and is being dealt with in the lower court.

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