ANZ is arguing for a case taken by more than 550 victims of a Ponzi scheme to be thrown out of court.
Investors say they lost $115 million to Ross Asset Management and are suing for $80m in damages. They are accusing the bank of negligence for allowing it to happen.
They claim the bank either knew or should have known Wellington financial adviser David Ross was operating New Zealand's largest Ponzi scheme, which collapsed in 2012.
"We've got a very strong case. The bank has a very high threshold to establish the case is basically useless," says Ross Asset Management (RAM) investor group spokesman John Strahl.
Ross was released from prison last week, having been granted parole after serving six years of his nearly 11-year sentence for fraud.
An ANZ client for twenty years, investors claim the bank knew Ross' accounts were being operated suspiciously, using money from clients' investment accounts to pay back debt into another account at least 100 times.
"ANZ really did nothing at all to look after their interests during the time the Ponzi scheme was in operation," Strahl says.
ANZ denies this, saying it too was misled by Ross.
"There may be justifications for such a transfer. The mere fact that they occur doesn't indicate knowledge of a breach of trust," says Neil Campbell, a lawyer for the bank.
ANZ says the case lacks specific detail and should be thrown out of court.
The class action is being funded by a New Zealand-based litigation group, which specialises in such actions on a no-win, no-fee basis.
Investors will have their say in court tomorrow.