Longtime David Bain supporter Joe Karam has filed a defamation claim against two people from a online group opposed to Mr Bain receiving compensation.
A defamation claim has also been filed against TradeMe, concerning postings on the website's message board.
Mr Bain was found not guilty at a retrial last year of the murders of his parents and three siblings in 1994.
In March this year, he lodged a compensation claim for the 13 years he spent in prison.
Mr Karam has confirmed defamation papers were lodged in the High Court in Auckland last month against Kent Parker from the Justice for Robin Bain group, another individual, and TradeMe.
Mr Parker has issued a statement saying the defamation claim is improper and vexatious.