The federal government is facing a negligence claim from more than 500 people impacted by the 2007 horse flu outbreak.
Law firm Maurice Blackburn said on Wednesday it had filed the class action in the Federal Court on behalf of 550 people "for losses arising" from the equine influenza (EI) outbreak.
It said the claim would allege the federal government "negligently caused the EI outbreak that devastated the horse and racing industries after the virus escaped".
Those signed on to the claim include racehorse owners, horse breeders, horse racing clubs, equestrian clubs, horse transporters, jockeys and trainers.
The law firm said hundreds of people suffered "significant financial loss" flowing from the outbreak.
Maurice Blackburn principal Damian Scattini said the Australian Quarantine Inspection Service (AQIS) had failed to ensure proper quarantine and biosecurity measures to protect the horse and racing industry.
"The failings of AQIS are well known, something confirmed by the Callinan Inquiry in 2008," he said.
The class action is being bankrolled by litigation funder Argentum.