Whistleblower Richard Boyle has been hailed a "superhero" after striking a plea deal under which he will avoid jail.
The 49-year-old has admitted to four criminal charges linked to his exposure of unethical debt recovery practices at the Australian Taxation Office.
Boyle appeared in the Adelaide District Court on Tuesday, where he pleaded guilty to disclosing protected information to another entity, making a record of protected information, using a listening device to record a private conversation and recording other people's tax file numbers.
The Commonwealth Director of Public Prosecutions withdrew a further 15 charges, while another five charges were dropped in March.
Outside court, Whistleblowers Justice Fund founder Rex Patrick said Boyle had "pleaded guilty to helping all Australians by disclosing poor conduct by the tax office, who were stripping funds from businesses who were in distress".
"He should be wearing a big S on his chest, as a superhero, instead of a conviction," the former senator said.
All of the charges Boyle admitted were criminal offences with both financial penalties and a maximum two-year prison sentence, he said.
"I understand that in pleading guilty he will avoid a custodial sentence, but he may well still be convicted, which is something he'll have to wear very heavily around his neck every time he applies for a job," Mr Patrick said.
Boyle, a former ATO debt collection officer, raised concerns internally about debt recovery practices in October 2017, when he grew worried about operations in the tax office.
Believing his complaints had been ignored, he went public on the ABC's Four Corners about the tactics used against taxpayers who owed the ATO money.
"This has been eight long years for Richard and it's a disgrace," Mr Patrick said.
"The message being sent by the government is if you blow the whistle, we will pursue you to the end."
Outside court, Boyle hugged supporters, including his wife, Louise Beaston.
The Human Rights Law Centre's Kieran Pender said it was a "heartbreaking day for Richard Boyle and whistleblowers in Australia".
"He should never have been prosecuted, and his case clearly demonstrates how our laws are failing to protect people who bravely speak up," he said.
"Prosecuting whistleblowers has a chilling effect on truth and transparency, and sends a clear message to prospective whistleblowers that if you speak up you will face punishment.
"The re-elected Albanese government must urgently reform the law to prevent a repeat of this prosecution and commit to establishing a federal Whistleblower Protection Authority."
Mr Patrick said the inspector-general of taxation had "basically vindicated Richard's calls, and the laws were changed".
"Richard has done a great service to this country," he said.
Last year, the SA Court of Appeal ruled Boyle was not protected by federal whistleblowing laws - because the charges related not to his whistleblowing, but steps Boyle had taken in preparation to blow the whistle internally, including taking photos of documents and recording conversations.
Boyle returns to court for sentencing submissions on August 1.
