Two local authority pension funds are suing Royal Bank of Scotland (RBS) for compensation.
Merseyside and North Yorkshire councils both accuse RBS of withholding how much trouble the bank was in before its government bail-out last year, according to the BBC.
The legal action against RBS, which has declined to comment, has been launched in the US, as that is where RBS did much of the business that caused its troubles. The councils will be represented by Cherie Booth QC, wife of former prime minister Tony Blair.
The move has opened up the case for other UK pension funds affected by the banking crisis to take similar legal action.
RBS accepted a £20bn bail-out package from the government in exchange for a 58% stake in the bank, which was subsequently increased to 68%.
The bank is planning up to 2,300 job cuts, it emerged last month.