Swiss banks systematically hid and destroyed records of bank accounts from the Holocaust period, thus preventing their owners from claiming their money and assets, according to a lawsuit set to be filed next week.

During the Nazi regime in 1933-1945 some 7 million bank accounts were created in Switzerland. An estimated 60,000 of them were opened by Jews in a bid to salvage their property from the Nazis, with the intention of reclaiming it after World War II.

Open gallery view Credit Suisse bank in Zurich. Credit: AP

Years later it emerged that the records of some 3 million of these accounts had disappeared and been destroyed.

"They all disappeared and were burned. They destroyed the evidence," says attorney Roland Roth, an expert in international law, who is preparing to file a massive suit against the Swiss banks on behalf of two Israeli clients.

The wholesale destruction of records was first uncovered by Swiss whistle-blower Christoph Meili. While working as a night guard in UBS 15 years ago, Meili reportedly discovered that bank officials were shredding documents related to the accounts of deceased clients whose heirs' whereabouts were unknown.

In Roth's estimate, the banks owe Jewish heirs $6 billion, based on what their accounts would have been worth if they had survived to this day. "I believe before the Holocaust there were at least 30 more people - apart from the two I represent - who held a great deal of property in Switzerland. But they probably didn't leave evidence to enable claiming their assets," he said.