External legal costs for the prosecution had reached $2,442,643 as of February 22 this year, the Attorney-General's Department revealed in response to questions on notice from Greens senator David Shoebridge.

This includes $337,826 of external legal costs for the Commonwealth Director of Public Prosecutions.

McBride, a former military lawyer, has pleaded guilty to three charges relating to the theft and disclosure to journalists of classified documents, which detailed alleged misconduct by Australian troops in Afghanistan.

He is still awaiting sentencing in the ACT Supreme Court.

Human Rights Law Centre senior lawyer Kieran Pender, who has been a key voice in calls for whistleblower reform, has said the costs raise questions of the Albanese government.

"I think these revelations around the money spent prosecuting the Afghan files whistleblower mark a continuation of money that this government and the last government are spending, prosecuting people who have helped expose wrongdoing," Mr Pender said.

"Expenditure that's not in the public interest."

He said the sum "raises real questions about why this government, like the last government is continuing to oversee the prosecution of whistleblowers".

Asked about the legal costs, a spokesperson for the Attorney-General's Department said, "The Australian government is committed to appropriately protecting sensitive and highly classified information in court proceedings while ensuring the open and proper administration of justice."

"As the matter involving Mr McBride remains before the Court, it would be inappropriate to comment further."

The Commonwealth Director of Public Prosecutions is required by policy to consider public interest before commencing prosecution.

It is understood the legal fees for McBride's case are related to the classified nature of information involved.

Advocates, including Mr Pender, had previously called on the Attorney-General to intervene in McBride's prosecution, as he did in the case of Bernard Collaery.

Mr Collaery was accused of revealing classified information about an alleged Australian spying operation in Timor-Leste, and faced five charges alleging breaches of the Intelligence Services Act.

In July 2022, the Attorney-General intervened to discontinue the prosecution - using powers in the Judiciary Act for the first time in 120 years - citing Australia's national interest.

In a speech delivered in November 2023, Mr Dreyfus referenced the "exceptional circumstances" for that step, and told parliamentarians, "... if the Commonwealth Attorney-General intervened in a prosecution as a result of public or political pressure, that could have a range of far-reaching consequences".

While the Albanese government has introduced some reforms to whistleblower protections, including increasing oversight of reprisals against those who speak up, advocates have called for a whistleblower protection authority to be established.

"This is money that would have been far better spent setting up a body that proactively protects rather than prosecutes whistleblowers," Mr Pender said.

"Labor at the 2019 election said it was going to set up a whistleblower protection authority, so why don't we have one?

"It's an important idea [and its] time has well and truly come.

"It would be far better for this government to spend its time and its money, establishing the institutional structures that can protect whistleblowers moving forward, rather than continuing to oversee these prosecutions."

Senator Shoebridge backed the calls for the independent authority.

"We have individuals facing incredibly well-resourced public authorities, and sometimes even entire governments," he said.

"It goes without saying that Australia is desperately in need of an independent whistleblower authority so that they have someone in their corner who can help them in situations like this."