The former prime minister of Timor Leste, Xanana Gusmao, says he wants to travel to Canberra to give evidence in court on behalf of former spy Witness K and lawyer Bernard Collaery if their prosecution continues.

Mr Gusmao has told Four Corners his evidence is likely to embarrass previous Australian governments in relation to the 2004 intelligence operation in which the Dili offices of the prime minister Mari Alkatiri were bugged by Australian foreign agents during treaty negotiations over oil and gas in the Timor Sea.

“I already promised to them, if it was not a secret trial, I will go to be their witness,” Mr Gusmao told Four Corners.

When asked what he would reveal in court, Mr Gusmao said, “All the information that I know.”

Witness K is a former intelligence agent who was involved in the Dili bugging operation in 2004. Mr Collaery is his former lawyer.

The pair are facing potential jail sentences after being prosecuted for allegedly conspiring to share secret information with the government of Timor Leste over the spying operation.

Mr Collaery faces four further charges over speaking to ABC journalists about the matter following an ASIO and AFP raid on his home and office.

Senior lawyers and crossbench politicians have expressed concerns about the prosecution and the secrecy surrounding the trials against the two men, which are being run under the National Security Information Act.

The NSI Act was introduced in 2004 to deal with classified and sensitive material in court cases. It has been used predominantly for terrorism trials and allows certain evidence and information to be heard in a closed court.

Anthony Whealy QC, a former judge who presided over the Lodhi terrorism trial, the first case heard under the NSI Act, has questioned the use of the act in this case.

Supporters of Bernard Collaery and Witness K protested outside the Supreme Court this month. Photo: AAP

“This could be one of the most secretive trials in Australian history,” he said.

“I don’t think they [the NSI laws] were designed for this sort of case at all. I don’t think they’re designed for cases involving whistleblowers, journalists, or the lawyers for whistleblowers,” Mr Whealy said.

Stephen Charles QC, a former judge of the Supreme Court, who as a barrister has acted for both ASIO and ASIS, has also spoken out.

“It is difficult to imagine any justification for these proceedings taking place in secret,” he told Four Corners.

“Everyone who reads the newspapers is aware that ASIS officers, entered and bugged the Timorese cabinet premises.

“Everyone is aware that the result of bugging those premises was that Australia got a huge and very unfair advantage in the negotiations being carried out between Timor and Australia.”

Bret Walker SC, the former independent monitor of Australia’s national security legislation, who has previously acted for Witness K in another matter, told Four Corners it was important that the principles of open justice were upheld.

“Every Australian, I imagine, is interested to know that Australian authorities will be held to account. That’s difficult to do if a trial, at the pointy end, will be held secretly,” he said.

Attorney-General Christian Porter has issued a secret certificate limiting the disclosure of certain information and evidence in court that is considered prejudicial to national security.

Ultimately, it is up to a judge or magistrate to decide what is heard in open court.

Lawyer Bernard Collaery says he doesn’t know what he’ll be able to say in court. Photo: www.cclaw.com.au

But Mr Collaery said the NSI Act had already impacted on his defence and his ability to instruct his lawyers.

“I don’t know what I’m going to be allowed to say in court. I’ve only just been allowed to speak to my lawyers after 18 months, or whatever it is. I’m now able to speak to my lawyers, but I’m circumscribed even in what I can tell my own lawyers. It’s amazing,” he said.

In a statement, the Attorney-General told Four Corners he believed the courts would get it right.

“I have confidence in the judicial process and that the court will strike the right balance between the need to protect national security and the principle of open and transparent proceedings in this matter,” the statement said.

“I have previously expressed the view that as far as it is possible, any legal proceedings in this matter should be conducted in open court, and this remains my view.”

The prosecution of Witness K and Mr Collaery is different from most legal cases in that it requires consent from the Attorney-General before the prosecution can go ahead.

That is because the case involves alleged breaches of the secrecy provisions of the act that governs Australia’s foreign intelligence agency ASIS – the Australia Secret Intelligence Service.

Mr Porter decided in May last year to prosecute, within six months of taking office. Butt his predecessor, George Brandis, did not give consent in the two years and three months after he was asked to do so by the Commonwealth Director of Public Prosecutions.

Mr Collaery maintains he is innocent of all charges.

Witness K has indicated he intends to plead guilty, subject to agreed facts.

If the prosecution agrees, that plea would be limited to a narrow admission that all he did was execute an affidavit in anticipation of hearings in an international court.

-ABC