Rex Patrick continues the fight for East Timor cabinet papers at secret AAT hearing

The self-described "transparency warrior" is taking on the federal government to overturn a secrecy exemption placed on cabinet documents from 2000 by the former attorney-general and kept in place by Attorney-General Mark Dreyfus.

The details could show Australian spies were listening in on the East Timorese government from as early as 2000, four years before an alleged cabinet room bugging under the Howard government sought to gain advantage during negotiations over lucrative oil and gas reserves.

The National Archives of Australia suppressed the release of the documents in its 2000 cabinet papers, citing their publication could potentially harm relations with "the current government of a foreign country".

A heavily redacted version of the documents was released earlier this year showing the Howard government was concerned Australia's access to the reserves in the Timor Sea would be negatively impacted by the small nation's bid for independence.

But Mr Patrick believes they should be released entirely in the name of transparency, having taken it to a court battle with the Administrative Appeals Tribunal.

Representatives from the National Archives of Australia will present their arguments against the unredacted documents' release behind closed doors on Thursday morning with the former senator being barred from sitting in due to their sensitivities.

Mr Patrick said it made an uphill battle even tougher, but he wasn't going to back down.

"When you are involved in a fight with the [National] Archives about its refusal to grant access to historical documents, you start with one hand tied behind your back because you aren't able to see the contents of the documents you're arguing about," Mr Patrick told The Canberra Times.

"When they close the court so you can't even hear their argument, they tie your other hand behind your back.

"It's hardly a fair fight, but they seem most comfortable with that idea."

Documents filed in court by Mr Patrick earlier this year have already revealed comments allegedly made by former foreign affairs minister Alexander Downer, describing East Timor as an "open book" to Australia in 2000.

The comments were allegedly made to a then-Labor staffer while Mr Downer and former Labor MP and activist Laurie Brereton were on a plane back to Australia.

An affidavit by former Timor-Leste president Xanana Gusmao also disclosed he held suspicions Australia had been spying on him from as early as 1999 based on a warning from a senior United Nations diplomat.

Mr Gusmao, who was president between 2002 and 2007 before becoming prime minister until 2015, said Timor-Leste "responds well to truth, dialogue and transparency", referencing the country's improved relations with Indonesia.

Labor struck down a motion by Mr Patrick to refer the saga to a parliamentary committee late last year with now-Finance Minister Katy Gallagher instead committing to launch an inquiry, if elected, and to amend laws to allow committees to look into foreign intelligence agency, the Australian Secret Intelligence Service.

It's yet to announce its plans since forming government.

The spying saga was disclosed in 2013 after Timor-Leste took its concerns about the bugging operation to the Permanent Court of Arbitration in The Hague where a former Australian intelligence officer, known as Witness K, was invited by Timor-Leste to give evidence.

The office of his lawyer, and former ACT attorney-general, Bernard Collaery, was raided and he was later charged with sharing protected information in breach of the Intelligence Services Act.

The charges against Mr Collaery were dropped earlier this month after Mr Dreyfus ordered Commonwealth prosecutors to discontinue the case.

Mr Patrick last year described the original incident, and the subsequent prosecution of Mr Colleary, as a "disturbing set of circumstances", which needed scrutiny in order to explain Australia's actions against an impoverished neighbouring country.

He said he just wants to see the secrecy end.

"The time for secrecy around the Australian government's attempts to defraud the newly-independent nation of Timor-Leste of their oil and gas resource has come to an end," Mr Patrick said ahead of Thursday's secret AAT hearing.

"The Timorese want that too, and whilst there is still secrecy, there will always be an elephant in the room when officials from the two countries meet."