Arnold in a shock blast at the new UBS chief

Olivant, the specialist financial investment vehicle run by Arnold, who was once chief executive of UBS, has bought a 0.7% stake in the bank and is stirring up pressure for it to appoint a fully independent chairman in the wake of its £19 billion of losses on subprime assets.

For the first time, Olivant today named three potential candidates for the job, all of whom, as Arnold has suggested, are highly qualified Swiss bankers. They are:

Josef Ackermann, 60, chief executive of Deutsche Bank, who has massively revived the German bank since he took its helm in 1996;

Hans-Joerg Rudloff, 67, chairman of Barclays Capital and doyen of the eurobond market, which he virtually created when at Credit Suisse;

Markus Granziol, 56, a former senior colleague of Arnoldwhen he was chairman of UBS Warburg and now chairman of Eurex.

But, according to Olivant, none of these people has been approached even on an informal basis. In the meantime, it claims, Kurerwas nominated to take over from Marcus Ospel as the head of UBS on the last possible day before the bank's annual meeting on 23 April. That gave no one else the chance to be nominated and the chairmanship cannot be changed for another year.

Arnold is still expecting a meeting with UBS senior non-executive director Sergio Marchionne before the annual meeting but said today that the search for a new chairman had to be announced before then. He said Kurer, UBS's top lawyer, had to be considered an insider rather than an independent chairman of the bank. He added that Kurer "has no banking, strategic, credit or market risk experience - all skills which are of critical importance given the situation in which UBS finds itself".

But Kurer claimed Arnold was being "discriminatory" against lawyers and added: "I have not accepted this job on an interim basis. The company needs leadership and needs to know who is at the helm." Arnold said Kurer should only be allowed to become interim chairman of the bank while the formal search for a full-time replacement takes place.

Olivant's statement said: "We do not believe Mr Kurer is the best qualified, or right, candidate to take over as chairman of a bank with a complex business model, that has recorded the largest proprietary trading losses in history, has 85,000 employees, a balance sheet of over $2 trillion and significant challenges and opportunities."