Fairfax’s top investigative reporters have slammed Gina Rinehart’s attempts to force her biographer, Adele Ferguson, to hand over all correspondence with the mining magnate’s son, John Hancock. Some want influential commentators such as Andrew Bolt to rally to her cause.

The Supreme Court of Western Australia, at Rinehart’s request, has issued a subpoena demanding Ferguson hand over any emails, text messages, notebooks related to conversations and interview recordings between Ferguson and Hancock since September 2011. Ferguson, a senior business writer at The Age and The Sydney Morning Herald, could face jail unless she complies with the subpoena by the end of the month.

The Age investigative reporter Nick McKenzie told Crikey it’s “outrageous” that Rinehart, who owns around 15% of Fairfax shares, would make such a demand.

“It makes one wonder whether she cares at all about journalism,” McKenzie said. “This goes to the core of what we do …  People have long speculated about what Gina Rinehart’s motivations are [in investing in Fairfax], and this shows they aren’t savoury.”

McKenzie is calling on rival publications and free speech advocates such as Herald Sun columnist Andrew Bolt, who was found guilty of racial vilification in 2011, to support Ferguson publicly.

“Andrew Bolt has learnt first-hand what it’s like to have one’s journalism restricted by a court and how time-consuming it can be. There is not a journalist in the country who wouldn’t be concerned about this,” he said.

Fairfax’s national business editor Mark Hawthorne queried on Twitter why Bolt, a prolific blogger, has kept silent on the issue. Bolt hosts a Sunday program on Channel Ten — Rinehart, who is known to be a fan of his work, is a major shareholder of the network.

The Australian Financial Review‘s editor-at-large Pamela Williams told Crikey: “It is a pretty remarkable situation for a media company’s major shareholder to demand a journalist reveal their sources. This really is an inversion of everything that someone with a commitment to media should stand for.”

Williams’ Fin Review colleague Neil Chenoweth said: “The imperative to protect your sources is intrinsic not only to reporters but to the media business as a business. There are commercial consequences if you undermine that safeguard for sources. For a would-be media proprietor to ignore this raises questions whether their investment is a commercial one, or to further personal goals.”

Fairfax journalists Ben Cubby and Paddy Manning are among those who have signed a change.org petition demanding Rinehart withdraw the subpoenas issued against Ferguson.

McKenzie says it could cost Fairfax hundreds of thousands of dollars to fight the subpoena — “money that should be spent on journalism”. McKenzie and colleague Richard Baker are currently fighting two attempts for them to give up confidential sources: one over stories about property developer Helen Liu, the other on their reporting of the Securency note-printing scandal.

Kate McClymont, an investigative journalist at The Sydney Morning Herald, says although Rinehart has a legal right to demand the information, maintaining the confidentiality of sources is vital. Although Ferguson’s book and Fairfax articles contained on-the-record quotes from Hancock, this doesn’t mean their interviews did not contain confidential information.

“Interviews are never quite as clear-cut as they seem,” McClymont said.

Western Australia passed “shield law” legislation last year enshrining journalists’ right not to reveal their sources in court. However, a court can order a journalist to reveal a source where the public interest in the administration of justice outweighs the harm to the source.

Ferguson told the ABC this morning she would go to jail rather than give up her correspondence with a source.

UPDATE: On his blog this afternoon, Bolt posted this update: “I like Rinehart and do not understand the legal argument here, but this is not a good look for someone on the board of the company employing the journalist.”