UK insurance and financial services firm Prudential is to promote Tidjane Thiam, chief financial officer, as chief executive following the resignation of Mark Tucker, the firm has announced. 

Views have diverged on why Mr Tucker stepped down unexpectedly after four years, but he has moved to quash speculation that a disagreement over whether to bid for assets being sold in Asia by the beleaguered US insurer AIG had caused a row. Prudential has not commented on reasons for his departure.

"On AIG, we did not submit a bid in the process," he told The Independent. "Our view is that we could not get to the value criteria that we had in place."

In his 25 years at Prudential, Mr Tucker worked across the business in the UK, US and Asia, and was chief executive of Prudential Corporation Asia. He was appointed group chief executive in May 2005.

Mr Thiam joined Prudential in March 2008 from Aviva, where he was an executive director and chief executive of Aviva Europe. He also worked for six years in leadership roles including group strategy and development director.

Prudential has £249 billion ($359.2 billion) in assets under management, as at 31 December 2008.