John Stewart, the Scottish head of Clydesdale Bank parent company National Australia Bank, is to be replaced, the company announced yesterday, just days after he had to admit to an extra A$830m (£99m) of losses on investments hit by the US sub-prime crisis.

Stewart has headed up the business since the beginning of 2004 following a five month stint overseeing the Clydesdale as the company's chief executive for Europe.

But he was widely criticised last week following the announcement of the additional provisions on the investments which came just days after NAB conducted a bond issue.

He is to be replaced by Cameron Clyne, who runs the company's New Zealand business. Clyne will become chief executive-designate from October 1 until Stewart formally finishes his tenure on December 31.

Stewart is expected to leave with a pay-off estimated at some A$10m (£4.7m), although the bank did not confirm details yesterday.

NAB yesterday said Stewart's retiral had long been expected and was unconnected to the losses. Clyne said his priority would be to focus on the company's risk management.

Stewart joined the company from Barclays where he was deputy chief executive. He gained the position after the bank bought the Woolwich, where he was chief executive, leading its conversion from a building society into a FTSE-100 listed company.

Lynn Peacock, who currently heads Clydesdale, had previously been talked of as a successor to Stewart.

She had long been an ally of Stewart, serving as his chief operations officer at the Woolwich.

She rejoined him at NAB as executive director in 2003, taking over the UK operations a year later.

A Clydesdale spokesman said yesterday that Peacock has a "good working relationship" with Cameron, having worked with him on the group executive since he took on the New Zealand job last year.