Australia lender Westpac received a class action against an asset management and insurance arm it owns, accusing it of charging thousands of pension fund customers for services they never received.
Clients claim to have been "short-changed" out of their retirement savings for more than a decade.
"We believe Westpac Life provided no service that could justify it retaining such a large part of the returns generated from members' money, and we want the difference paid back to members," said Nathan Rapoport, the Slater & Gordon lawyer managing the case.
We believe Westpac Life provided no service that could justify it retaining such a large part of the returns generated from members' money, and we want the difference paid back to members"
He said, in recent years, Westpac Life had earned "reasonable returns" (2.5%) but decided to only pass on half of it (1.3%) to the members.
Rapaport estimated that the total compensation his clients are seeking from the Westpac companies could range in the tens of millions of dollars.
On an individual basis, the plaintiff lawyer said some of his clients may be owed "thousands" of dollars each.
The legal action against Australia's second-biggest bank, revealed by Westpac to the stock market, is one of almost a dozen lawsuits resulting from a Royal Commission inquiry that found evidence of widespread misconduct in the financial sector.
In a statement to the ASX, Westpac said: "The damages sought by the claim are unspecified", and BT and Westpac Life will be defending against the class action.
Slater and Gordon has already filed similar claims against the country's biggest lender Commonwealth Bank of Australia and financial planner AMP. It has said it is seeking more than A$100m against CBA, while it has also not specified damages against AMP.
The case is funded by Therium Capital Management, a UK-based litigation funder with offices in Australia.