Prosecutor Dario Zanni has appointed a magistrate to investigate the complaint filed by Franck Berlamont, head of Geneva Partners, an independent asset manager, the news service said.

Optimal clients lost about €2.3 billion ($3.2 billion) on investments with Mr Madoff, who has admitted to fraud after running a massive Ponzi scheme and is awaiting sentencing later this month. His case has rocked the financial industry and raised concerns about the levels of due diligence carried out by financial intermediaries into Mr Madoff's scheme.

Optimal’s prospectus said it managed the firm’s Madoff- linked investments and had conducted a full review of Madoff, which included analysing trades, visiting his New York office, and interviewing his chief risk and chief financial officers, Mr Berlamont was reported by the news agency as saying. Now the Geneva-based unit of Spain’s biggest bank says it isn’t liable for the losses because Madoff managed the investments.

“I was scammed by my neighbours,” Mr Berlamont was quoted as saying.

A Santander spokesman declined to comment, the news agency said.

In late May, it was reported that Santander will pay $235 million to settle claims against two hedge funds managed by its Optimal subsidiary.