At least two of Australia's financial powerhouses face the threat of class actions for ripping off their superannuation clients.

Plaintiff law firm Slater & Gordon on Tuesday revealed it was seeking expressions of interest for a class action against financial institutions following damaging revelations about their treatment of customers, saying they collectively owed Australians "more than one billion dollars".

Commonwealth Bank-owned Colonial First State and AMP are the first targets of the proposed action. Credit:Dean Lewins / AAP

The company said the first targets would be the Commonwealth Bank of Australia-owned Colonial First State and AMP, but at a press conference on Tuesday it also mentioned it might look at adding IOOF in future, as well as "most of the major retail funds".

There would be a series of announcements over the coming "weeks and months", it foreshadowed.