The Commonwealth has spent more than $7.6 million prosecuting three whistleblowers. 

Officials from the Attorney-General's Department revealed the cost under questioning from New South Wales Greens senator David Shoebridge this week. 

The Attorney-General's Department revealed that by the end of January, a case against Canberra lawyer Bernard Collaery and an ex-spy known by the pseudonym “Witness K” had cost the Commonwealth $5,510,829. The case has now been dropped. 

The department also gave details of prosecutions against David McBride (who is being prosecuted for allegedly leaking top-secret defence information to the ABC) and Richard Boyle (who blew the whistle on unethical debt recovery practices within the Australian Taxation Office). 

The McBride prosecution has reached $1,875,348, while Mr Boyle's case reached $233,171.

Senator Shoebridge said the department is using taxpayer funds for “monstering whistleblowers”.

“Is there some point at which … your department reviews the lavish use of public money to jail a whistleblower,” he asked.

“I'm not sure I would agree with your characterisation of lavish, it's a significant amount of money,” Attorney-General Department Secretary Katherine Jones responded.

The Albanese Government is reviewing Commonwealth whistleblowing protections, but is maintaining the pursuit of Mr McBride and Mr Boyle at the same time.