More than 50 currency speculators have been told by Denmark-headquartered Saxo Capital Markets to pay up millions of dollars to cover losses associated with last week’s surge in the value of the Swiss franc, a report says.

Saxo Bank has confirmed that a number of its clients have suffered losses due to last Thursday's massive surge of the Swiss franc against the euro, but said its own proprietary trading position has not taken a net loss.

The bank did not directly comment on media reports that dozens of Singapore-based clients have been told by Saxo Bank to cover losses.

“Due to the sudden material increase in the price of [the] Swiss franc on 15 January 2015, a number of Saxo Bank’s customers ended up with insufficient margin collateral to cover their losses on positions in Swiss franc,” Saxo Bank said in an emailed statement when questioned by this publication.

“Saxo Bank is liaising with these clients to settle such unsecured amounts. It is expected that some customers will not be able to the settle the balance in full and that the bank will incur losses in this respect. However, even in the unlikely event that Saxo Bank would not be able to recover any of the outstanding amounts, Saxo Bank would still fulfil its regulatory capital requirements,” it continued.

“Saxo Bank generally only holds insignificant proprietary positions – including to Swiss franc, and Saxo Bank did not incur any net losses on proprietary trading during this event,” it added.

According to a report by the Straits Times of Singapore, more than 50 currency speculators in Singapore have been told by Denmark-headquartered Saxo Capital Markets to pay up millions of dollars to cover losses associated with last week’s surge in the value of the Swiss franc. Letters have been sent by Saxo to clients about the losses, the newspaper said.

The report said the firm is demanding that the clients, some of whom were betting on euro-franc movements, make good on their losses by a specific time or "face action". In the letter, it reportedly said it had exercised its right to close out open positions, given "adverse movements in the financial markets" on 15 January.

It has already been estimated that banking groups Citigroup, Barclays and Deutsche Bank have suffered losses of up to $400 million from last Thursday’s shock decision by the Swiss National Bank not to cap the Swiss franc against the euro at 1.20. The Swiss franc surged by more than 40 per cent at one stage. Julius Baer, the Swiss bank, has announced it suffered no losses; Credit Suisse said it has suffered no material loss.

A hedge fund run by Everest Capital has reportedly been wiped out by the drama.

The report, quoting lawyers, said a key issue is whether Saxo is entitled to requote prices or set different rates, and retrospectively apply those rates to concluded contracts. An investor reportedly told the newspaper that because of the requote, the losses on €750,000 worth of forex contracts ballooned overnight from €6,250 to €144,000.