NM Rothschild is being sued by four pensioners over a Spanish property investment scheme that is said to have gone sour.
The Sunday Times reports papers have been filed at the High Court which claim a Rothschild employee gave a presentation in 2005 about investing in an insurance firm.
The pensioners say this led to them taking out mortgages of up to 75 per cent against their homes in Spain.
The pensioners put the cash into Aspecta Assurance, aiming to make a profit and save money on Spanish inheritance tax.
However, the group now claims the scheme did not perform as advertised, leading to them falling behind on their mortgage repayments.
Michael and Roberta Carney took out a loan of £247,500 in 2006 and claim to have lost around £105,422.
Brian and Pamela Fox say they have lost £213,000.
The pensioners say Rothschild took advantage of their lack of investment knowledge.
However, the bank denies the legitimacy of the claims and plans to contest them.