Mr Karam said he has issued two claims at the High Court in Auckland against members of Justice for Robin Bain Group (JFRB) and counterspin.co.nz, and TradeMe website.
He told NZPA one claim was against Vic Purkiss and Kent Parker from JFRB and counterspin, and the second was for an online trade site in respect to its message boards.
In a statement today, Mr Parker said the defamation claims were for things stated on the group's Facebook site, counterspin and TradeMe.
"The claims includes 194 citations involving 18 different people, and 12 items of alleged damage have been claimed."
"We will be defending Mr Karam's claim and maintain that it is improper and vexatious. We have a very good team in place and are confident of a positive outcome for the JFRB Group."
In his blog, Mr Parker said Mr Karam had given the group a defamation warning on Christmas Eve.
Mr Karam confirmed he did, but refused to comment any further.
Mr Parker said in response to the warning the group had made its Facebook page private and on the counterspin site, "great care had been taken to screen out any content that is potentially defamatory".
No one from the JFRB Group was available for further comment pending the judicial process.
TradeMe spokesman Paul Ford said it was aware of the claim against it and was seeking legal advice. He declined further comment.
JFRB is an activist group against David Bain, who was convicted in 1995 of murdering his parents, Robin and Margaret, two sisters Laniet and Arawa and brother Stephen in their Dunedin home.
In 2007 the Privy Council quashed his convictions on the grounds of a substantial miscarriage of justice and ordered a retrial.
He was found not guilty at a retrial in June last year, after his defence team had argued that his father, Robin, had shot the other four family members before turning the gun on himself.
In March, Justice Minister Simon Power said he had received a letter from Mr Bain's lawyers formally notifying him of a claim for compensation for wrongful conviction and imprisonment.
JFRB started a petition against the claim and currently has 1540 signatures. They are still hoping to reach their 10,000 target.
