British-based investment company Olivant has raised its stake in Switzerland's biggest bank, UBS, despite earlier criticism of its management.

The firm now owns 2.5 per cent of the bank's capital, demonstrating what it called in a statement on Wednesday "its belief in the potential restoration of shareholder value through decisive action on the part of the UBS board".

Olivant announced in April that it had taken a 1.1 per cent stake in the bank, and its head, former UBS chief executive Luqman Arnold, called for the bank to reform and consider splitting up.

Arnold believed the move would help counter the effects of massive losses incurred in the United States subprime crisis. The proposal came after UBS announced writedowns totalling more than SFr40 billion ($38.3 billion) over nine months.

Olivant says that it now supports recent decisions taken by the bank's board, but that future strategy needs to be clarified to make UBS an attractive employer for bankers.

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