Fitzgerald, a 48-year-old former rugby star who was capped 34 times for Ireland between 1984 and 1992, declined to discuss the reasons for his surprise departure. "I'm going on to pursue other interests, " he said.

"There are no 'issues' behind my decision."

An Ulster Bank spokeswoman said the parting had been "amicable".

A former managing director of ICL Ireland, Fitzgerald was headhunted by First Active's former chief executive Cormac McCarthy in 2001.

As general manager for sales and marketing, he helped First Active to launch a series of product innovations including current account mortgages that save customers money by offsetting savings against their debts when calculating interest.

Fitzgerald followed his boss when McCarthy was appointed chief executive of Ulster Bank in 2003 after the �?�887m acquisition of First Active by Ulster's parent, Royal Bank of Scotland.

His promotion to the job of managing director for retail banking a year later was widely seen as confirmation of Fitzgerald's position in McCarthy's inner circle.