David McBride is facing five charges relating to the obtaining and disclosure of classified information about alleged misconduct by special forces troops.
Pre-trial arguments started in the ACT Supreme Court on Monday and the trial is expected to last three weeks.
McBride's lawyers contend his duty to disclose allegations of war crimes trumps his duty to abide by defence secrecy provisions.
Helen Haines said the case was happening while there's "a vacuum in whistleblower protection laws".
MPs and human rights advocates continue to call for Attorney-General Mark Dreyfus to drop the prosecution, arguing it's not in the national interest to jail a whistleblower.
Independent MP Helen Haines said the case was happening while there was "a vacuum in whistleblower protection laws".
"He's fallen right into this gap where he doesn't have the protections that most people would expect," she told ABC radio on Tuesday.
"Someone who's done the right thing by blowing the whistle on wrongdoing should be protected.
"The prosecution needs to weigh up the public interest and I think the public interest is served by blowing the whistle on these types of horrendous events."
But Mr Dreyfus said using his powers to drop prosecutions that are conducted independently of the attorney-general's office would set a dangerous precedent of political intervention.
"One of the most important features of our criminal justice system is that the decision to prosecute is a matter for the independent Commonwealth Director of Public Prosecutions," he told parliament.
He said the power to order a prosecution be discontinued was "an extraordinary power that should be exercised only in extraordinary circumstances".
This was backed up by the fact it had only been used once in 120 years, he said.
"If the commonwealth attorney-general intervened in a prosecution as the result of public or political pressure, that could have a range of far-reaching consequences," he said.
"It could call into question the attorney-general's motives, it could politicise the prosecution process, it could undermine the independence of the Director of Public Prosecutions."
Mr Dreyfus said the second tranche of whistleblower reforms was being worked through and the government would be seeking views on how oversight and integrity agencies would function as well as the potential operation of a whistleblower protection authority or commissioner.
14°C