SYDNEY (AFP) - Australia's major media organisations on Monday joined forces to back publisher Bauer's appeal against the nation's largest defamation payout awarded to Hollywood actor Rebel Wilson, arguing the size of the damages could stifle public-interest journalism.

Newspaper publishers News Corp and Fairfax, radio station owner Macquarie and television broadcasters ABC, Seven and Nine filed the documents with the Victorian Court of Appeal.

Their joint lawyer Justin Quill said the six "unlikely bedfellows" were seeking leave to intervene in Bauer Media's appeal against the damages award.

"The fact six media companies have combined demonstrates how serious this issue is," he wrote in News Corp's Melbourne Herald Sun newspaper.

Mr Quill said the media organisations were appealing Justice John Dixon's decision to award Wilson A$3.9 million (S$4.1 million) in special damages and A$650,000 in general and aggravated damages.

The award was far higher than the statutory cap of A$389,500 for general damages, which has risen from A$250,000 since the ceiling was introduced under uniform defamation laws across all Australian jurisdictions in 2005.

Mr Quill said after the judge's decision, other plaintiffs pursuing court action against media companies were seeking aggravated damages - and therefore higher payouts - claiming that the cap did not apply to their cases either.

"The damages cap provides certainty and creates a fair balance between the competing interests of protection of reputation and freedom of speech," Mr Quill wrote.

"Freedom of speech is important and the media's ability to uncover dodgy politicians or expose unscrupulous business practices benefits society."

The Pitch Perfect star was awarded the damages against Bauer Media in September over magazine articles claiming she lied about her age and background to further her career.

Wilson has said she would give the money to charity.