An independent report into the outbreak, carried out by consultants Sapere, determined decisions made in breach of Biosecurity NZ's own statutory regulations allowed the disease into New Zealand, he said.
However, MPI says various studies have not been able to conclude how Psa entered New Zealand.
"There is no doubt in our minds that Biosecurity NZ was negligent in how it was protecting New Zealand from Psa and other risks from as far back as 2004," Mr Cameron said.
Mr Cameron said the legal challenge was not just for the kiwifruit industry but for those involved in all primary industries in New Zealand.
"What if [the border systems] failed and they let in TB or foot and mouth?" he said.
The Government was responsible for protecting the country from the disease but failed to do so, Mr Cameron said.
"The duty of care, if it's lost in the courts the repercussions throughout New Zealand is absolutely huge."
Mr Cameron said he was confident the case would be successful, based on legal advice.
He encouraged all growers and post-harvest operators who had been affected by the vine killing disease to join the action.
MPI released a statement saying they were aware of the potential class action but were confident the ministry had acted appropriately.
Various studies had not been able to reach a conclusion as to exactly how Psa entered New Zealand, it said. The statement said the ministry was not aware of the Crown being held legally liable for this type of biosecurity breach before.
New Zealand Kiwifruit Growers Incorporated also released a statement explaining the organisation was reviewing the details of the compensation claim to seek clarity about the legal base of the claim, the chances of success, how much it would cost growers to enter into the claim and what their liability would be if it was unsuccessful.
A Zespri spokesman told the Bay of Plenty Times the company was only informed of the class action suit yesterday and would like to study the details before drawing conclusions because it had not received any information from the growers involved.
Bay of Plenty MP Todd Muller said Psa was a huge issue in the area and he would be following the case with interest.
The committee
BOB BURT: Long established kiwifruit grower based in Te Puke.
JOHN CAMERON: Dairy farmer and kiwifruit and avocado grower.
ALLAN DAWSON: Aongatete managing director.
MURRAY GIBSON: Accountant based in Te Puke.Litigation team
ALAN GALBRAITH QC: More than 40 years' experience in commercial litigation.
MATTHEW DUNNING QC: More than 25 years' experience in general corporate and commercial litigation.
DAN PARKER: More than 23 years' civil litigation experience.