(REUTERS) -- Swiss National Bank Chairman Philipp Hildebrand is resigning with immediate effect after a scandal over a controversial currency trade made by his wife, the SNB said on Monday.

The SNB said in a brief statement that Hildebrand would speak about his decision at 1415 GMT at a media briefing in Berne and make available a number of unspecified documents.

Hildebrand's wife Kashya, a former hedge fund trader who now runs a Zurich art gallery, bought 400,000 Swiss francs ($418,000) worth of dollars on August 15, three weeks before her husband oversaw steps to cap the rise of the franc.

Hildebrand last week rejected calls to step down, saying he only learned of his wife's trade the following day, rejecting claims by the Swiss magazine Weltwoche that he had personally authorized the currency deal, which made a big profit.

($1 = 0.9564 Swiss francs)

(Reporting by Emma Thomasson)