Ulster Bank's chief executive Gerry Mallon has announced he is leaving the bank to "take up a new opportunity" with Tesco Bank in the UK.
Mr Mallon will replace Tesco Bank CEO Benny Higgins, who will retire in February.
Gerry Mallon, who is also chairman of the Irish Football Association in Northern Ireland, was Ulster Bank's CEO for just over two years.
In a statement this morning, Ulster Bank said Mr Mallon will remain in the CEO role while he serves his notice and while a replacement is identified.
"My decision to accept this role with another organisation was an enormously difficult one but it is an excellent opportunity for me and for my family," Mr Mallon said.
"I am grateful to the board, executive and staff of Ulster Bank for their unstinting support to me as chief executive and I wish them and the broader group every success for the future," he added.
Ulster Bank is owned by Royal Bank of Scotland.
Ulster Bank Ireland DAC Chairman Des O'Shea thanked Mr Mallon for his contribution at an important time for the bank and for working tirelessly on progressing its strategy.
He said that Mr Mallon will remain in place until the middle of the year to manage the transition with the Board and the Ulster Bank Executive Committee.
Founded in 1997 as a joint-venture with the Royal Bank of Scotland, Tesco Bank came under Tesco ownership in 2008.
The bank has grown since then and makes annual profits of £200m. It serves eight million bank accounts, mainly through outlets in Tesco supermarkets.
Commenting on the move, John Cronin at Goodbody Stockbrokers said that electing a young and energetic leader to target growth across the domain of financial services product in a world of burgeoning open access to banking data would seem to be "a sensible move".
But the Financial Services Union has criticised the departure of Mr Mallon from Ulster Bank.
Outgoing general secretary Larry Broderick said that he was "surprised and frustrated" at the departure.
"As our economy and financial sector recovers, leadership and long-term commitment is required at the helm of our banking system. The departure of a CEO after a short period of time doesn’t serve this purpose", Mr Broderick said ina statement.
He noted that Mr Mallon's tenure at Ulster Bank has seen a raft of branch closures as well as the tracker book crisis which is ongoing.
"RBS needs to radically review its approach to leadership in Ulster Bank. It also needs to agree a long-term strategy for the bank with staff and FSU," he added.
