Married couple
Philipp Hildebrand with wife Kashya, whose purchase of dollars caused controversy

The head of the Swiss Central Bank, Philipp Hildebrand, has stepped down amid a storm of suspicion following a currency transaction made by his wife.

The purchase of $504,000 by Hildebrand's wife in August, three weeks before the Swiss National Bank (SNB) imposed a currency cap, led to accusations of insider knowledge.

Although an internal investigation cleared Hildebrand of any wrongdoing, the currency deals were described by an independent auditor's report as "delicate".

The Swiss franc saw a flurry of investment from overseas throughout the global financial crisis, until it was capped in September at a record against the Euro.

However the move was three weeks after Hildebrand's wife, Kashya, who owns a gallery in Zurich, made the dollar purchase for herself and he daughter.

She defended the purchase, claiming she bought the dollars due to them being "ridiculously" cheap.

The bank said that Hildebrand would make a statement soon, as well as making a number of documents available.

Hildebrand has been with the central bank for eight years and was made president in 2010. In his time as head he lowered borrowing costs to zero while toughening financial regulation.

It is thought he will be replaced by deputy chairman Thomas Jordan, although this is unconfirmed.