The Ponzi scheme unravelled in 2012 and took $115 million of investors’ money with it.

Liquidators have been working through a process of requiring investors who withdrew money from the scheme to repay fictional returns they received.

Now investors are taking a class action against ANZ, which was Ross’ banker.

“ANZ Bank was David Ross’ banker and profited for over 20 years from this relationship,” said group spokesman John Strahl.

“As the largest bank in New Zealand and one of the biggest fund managers in Australasia we believe ANZ Bank knew how client accounts should have been operated and should have known that the way the RAM accounts were being operated was in breach of the laws.

“This was the finding of the New Zealand Financial Markets Authority and is why the regulator fought the ANZ Bank in New Zealand for three years so it could bring this to the attention of RAM investors.

“Banks just can’t turn a blind eye when it suits them. What we are seeing in Australia is that it is unacceptable not to know and understand your client.

“So whilst the ANZ Bank might be saying that it has no material issues in Australia, the RAM investor debacle is a clear example of failures in its New Zealand subsidiary to detect and act upon clear fraudulent behaviour. As a result the bank’s customers have been let down.”

The action against ANZ Bank is being fully funded by LPF Group, a New Zealand based litigation funder.

ANZ had been involved in a long-running court case with the Financial Markets Authority.

In April, ANZ lost its court bid to stop the Financial Markets Authority sharing its Ross files with third parties.