Mr Mack is quitting his post at the helm of Credit Suisse

Known as Mack the Knife for ruthless cost-cutting, he won respect for the way he steered investment banking arm CSFB after a dotcom-era scandal.

Mr Mack's co-CEO Oswald Gruebel will become sole CEO.

Credit Suisse gave no reason for Mr Mack's departure, which rumours ascribe to differences over potential mergers.

Credit Suisse said only that Mr Mack "has agreed with the Board of Directors not to renew his contract which will expire as of July 12".

Terse clues

"At this point in time we have no interest in pursuing a merger with another financial institution," said Credit Suisse chairman Walter Kielholtz, announcing the departure.

"Credit Suisse Group's financial performance has improved significantly as a result of strong measures taken by management," he added.

"Our goals are now to accelerate organic growth and strengthen the competitive positioning of our core banking businesses."

Mr Mack stepped into the top job at Credit Suisse in July 2001 when international banking institutions were reeling from stock market collapses at the end of the dotcom boom and the loss of that era's rich pickings in fees.

He moved fast to cut thousands of jobs to restore profitability.

Under his leadership, CSFB weathered the trial of its former Wall Street star, dotcom stocks analyst Frank Quattrone.

Mr Quattrone, 48, was found guilty of two counts of obstruction of justice and one count of witness tampering.