"In March alone he bought US dollars for 1.1 million Swiss francs," the paper said.
"It is classic [foreign exchange] speculation," claimed Philipp Gut, the paper's deputy editor in an interview. "The only option is for him to step down."
The SNB declined to comment on the allegations yesterday.
The newspaper reported that Hildebrand also bought more than US$500,000 in two transactions in August last year, weeks before the franc was devalued. It said that three weeks after the devaluation, Hildebrand sold his dollar holdings for a profit of 75,000 Swiss francs.
Gut said an employee from Bank Sarasin, the Swiss bank where the Hildebrands hold their private accounts, had told the newspaper that it was Hildebrand, not his wife, who had bought the dollars before the franc's devaluation.
Bank Sarasin revealed this week that it had sacked an unnamed employee who had breached Swiss banking secrecy laws by leaking confidential information on transactions "by the family of the president of the Swiss National Bank".
Switzerland decided to devalue its currency last year after businesses complained that its soaring value had hit exports. Tourism had also suffered as visitors were deterred by the country's high prices.
On September 6 last year, the SNB took the unprecedented step of pegging the franc to the euro at a minimum exchange rate of 1.20 Swiss francs. The surprise move caused the value of the franc to plummet.
Die Weltwoche's disclosures were the latest twist in an alleged banking scandal at SNB which has gripped Switzerland since shortly before Christmas when, in an apparent attempt to quell rumours about its head, the bank disclosed that Kashya Hildebrand had bought unspecified amounts in dollars for herself and her daughter on a purely private basis.
SNB later issued an unsolicited statement insisting that rumours of wrongdoing by Philipp Hildebrand were unfounded and the bank's rules against insider trading had not been breached.
The disclosures about Kashya Hildebrand's dollar purchases nevertheless prompted a media storm, which her public statements seemed designed to defuse.
- Independent