Richard Boyle’s case came before the South Australian Court of Appeal on Wednesday as he tried to overturn an earlier ruling that he should face a trial for releasing protected information.

Boyle is facing more than 20 charges relating to the release of protected material.

He claimed ATO staff had been instructed to use harsher debt collection tactics on some individuals and small businesses, including at times requiring banks to hand over money without taxpayers’ permission.

Boyle first raised his concerns through internal ATO processes before making a complaint to the tax ombudsman, and he later took part in a joint media investigation.

Follow-up reviews found his allegations were valid, while a federal parliamentary report also found the ATO had conducted a “superficial” investigation into his initial disclosure.

The case also includes allegations he taped private conversations without consent and took photos of taxpayer information.

Attorney-General Mark Dreyfus has declined to comment directly on the matter, but Tasmanian independent Andrew Wilkie on Thursday said it was extraordinary the government was continuing with a case launched under the previous Coalition administration.

“You would have thought the new government would see the sense in dropping the prosecution,” Wilkie said.

“This is the government that said that we’re going to review all of the public interest disclosure protections for whistleblowers and make them stronger – but in reality, they’re doing what they can to make them weaker.

“I call again on the government to drop this prosecution, to treat the whistleblower as a hero, not a villain.”

In recent civil proceedings in the South Australian District Court, Boyle argued his actions were consistent with the federal government’s Public Interest Disclosure Act, rendering him immune from prosecution.

But in March, Judge Liesl Kudelka dismissed his claim, ruling he was not protected by the act, effectively clearing the way for his criminal trial to proceed.

Asked about the case in federal parliament on Wednesday, Dreyfus said his powers to discontinue proceedings were reserved for “very unusual and exceptional circumstances”.

“Integrity and the rule of law are central to Australia’s criminal justice arrangements,” he said.

“Mr Boyle’s proceedings remain ongoing … it would be inappropriate to comment.”

But Victorian independent Helen Haines said it would be hard to find a more exceptional case.

NSW Greens senator David Shoebridge said it was clear Boyle had been telling the truth as his revelations had been backed by every review.

“The only thing that this continuing prosecution does, apart from putting Mr Boyle for an appallingly inappropriate criminal trial, is to send a chilling message to every single public servant in this country,” he said.

“That whether you see robodebt or a tax scandal, or other mismanagement, they will be prosecuted to the ends of this legal system if they dare tell the truth.”

-with AAP