Credit Suisse, which has been rocked by a spying scandal, announced Friday that chief executive Tidjane Thiam had resigned and would be replaced by the current head of the bank's Swiss operations.

"The Board of Directors of Credit Suisse Group has unanimously accepted the resignation of Tidjane Thiam and appointed Thomas Gottstein as the new CEO of Credit Suisse Group," the bank said in a statement.

Credit Suisse said Thiam would step down on February 14, a day after the presentation of the bank's fourth quarter and full-year results for 2019.

"I have agreed with the Board that I will step down from my role as CEO. I am proud of what the team has achieved during my tenure," Thiam said in the statement.

The announcement comes amid a swelling scandal over the bank's practice of spying on employees and others.

The banking giant was shaken by the discovery last September that surveillance had been ordered on star banker and former wealth management chief Iqbal Khan, after he announced he would move to its Swiss rival UBS.

And in December, an internal Credit Suisse probe confirmed that a second executive had been spied on by the bank.

But Switzerland's number two bank had maintained that just one senior leader, chief operating officer Pierre-Olivier Bouee who was forced out in October, was entirely to blame for both incidents and that rest of the top brass, including Thiam, had not been aware of the activities.

"I had no knowledge of the observation of two former colleagues," Thiam insisted in Friday's statement.

'I regret that this happened,' Thiam says
'I regret that this happened,' Thiam says AFP / Michael Buholzer

"It undoubtedly disturbed Credit Suisse and caused anxiety and hurt. I regret that this happened and it should never have taken place," he added.

The scandal broadened last weekend, when a Swiss weekly reported that the bank had also ordered surveillance on Greenpeace, including accessing militants emails, to try to find out when they were planning demonstrations against the bank.

In 2017, Greenpeace gatecrashed the bank's annual general meeting, with demonstrators unfurling a banner to protest links with companies behind a controversial oil pipeline in the United States.

Gottstein, who will take over the helm of Credit Suisse next week, has worked for the bank for more than two decades, and currently heads its Swiss operations and is a member of the executive board, the bank statement said.

"Based on his deep and comprehensive experience in our business and in view of his impressive performance as head of our Swiss bank and his respect amongst our clients and employees, Thomas Gottstein is excellently positioned to lead Credit Suisse into the future," company chairman Urs Rohner said in the statement.