Hundreds of people hit by the equine influenza outbreak that devastated the race horse industry in 2007 have joined a class action against the Commonwealth.

Maurice Blackburn Lawyers partner Damian Scattini says the outbreak, traced to an Australian Quarantine and Inspection Service (AQIS) station at Eastern Creek in NSW, was caused by negligence.

He says AQIS is accountable because it wasn't following its own rules at that facility.

"They would go from wherever they were in their street clothes, visit a horse, and then leave without changing or showering, then go and see other horses," he told AAP.

"So the inevitable happened."

More than 600 people have joined the action including those working in thoroughbred racing, harness racing, equestrian events, transporters and bookmakers.

Mr Scattini says trainer Robin Hoskings had a harness racing stallion, Lively Exit, which was not yet in his prime but had won $250,000 in prize money.

Lively Exit contracted EI in 2007 and died within three months.

"It's a devastating loss for the family, that guy waited his whole life to breed a champion and then it was taken away from him," Mr Scattini said.

The amount of compensation to be sought is still uncertain, but Mr Scattini estimates it to be many times more than the $220 million in assistance provided by the federal government in 2007.

The case will be brought in the Federal Court in Sydney in February.