By Dominic Giannini in Canberra

Recovering from a brain aneurysm that left him fighting for life, Dirk Fielding had to contend with the taxman skimming his accounts and threatening his business when he woke.

Mr Fielding does not dispute owing money to the Australian Tax Office after falling behind in his finances, before the medical episode left him on life support for a week and intensive care for a month.

The ATO began to garnish his business accounts, which he said left him financially vulnerable as he was unable to work and facing the prospect of not being able to pay the employees of his publishing company.

Someone had also stolen $823,000 from the business, he alleged.

“I begged for help, I couldn’t talk to anybody and I sent through a fax and Richard Boyle received that fax and rang me up and said, ‘mate, let me look after this’,” he told AAP.

“He lifted the garnish and reversed everything and helped me out… Richard gave me a lifeline.”

Boyle now faces decades behind bars after being charged in 2019 with recording private conversations and documenting sensitive taxpayer information while gathering evidence about ATO debt recovery practices he said were too harsh.

Boyle has pleaded not guilty to 24 offences.

The former ATO official alleged employees were pressured to use aggressive money recovery practices, making an internal complaint before going public with his accusation in 2018.

Transparency advocates call him a whistleblower in need of protection after he blew the lid on heavy-handed tactics used by the ATO to recover debt.

His legal fortunes took a major hit on Thursday when the High Court refused to hear his appeal against previous court rulings that he didn’t have immunity from prosecution despite his lawyers arguing he should be covered by whistleblower protections.

It means he will stand trial, with the upholding of a South Australian court’s decision that federal whistleblower protections did not grant immunity for offences related to gathering evidence.

Mr Fielding said Boyle was genuine in what he was trying to do.

“It’s not in the public interest for the public to be prosecuted, there are no victims out there,” Mr Fielding said.

“It needs someone to sit down and turn around and say, this is just stupid, no one is going to benefit from it.”

The Human Rights Law Centre has called for the Albanese government to uphold a commitment to urgently reform whistleblower laws.

“Attorney-General Mark Dreyfus must ensure Richard Boyle does not go to jail for exposing wrongdoing at the tax office and urgently fix federal whistleblower protections,” senior lawyer Kieran Pender said.

“Whistleblowers make Australia a better place – they should be protected, not prosecuted.”

A spokesperson for the attorney-general said it would be inappropriate to comment as the matter was before the courts.

A directions hearing in South Australia on Monday is set to outline when Boyle will face trial.

A day later, lawyers for David McBride are set to appear before the ACT Supreme Court to challenge his prison sentence for leaking secret defence documents that exposed allegations of Australian war crimes in Afghanistan.

McBride’s appeal is set for a single-day hearing in March 2025.