Ruairí O’Flynn said he was quitting the board for personal reasons.

In a short statement, the bank confirmed Mr O’Flynn’s departure and said a search for his successor is underway.

The CEO of Ulster Bank told staff that there is no link between his resignation and the ongoing strategic review of the future of Ulster Bank’s business by parent NatWest.

Jane Howard said he joined the bank as chairman with broad expertise in financial services.

“He was ready to help us navigate all of the challenges and opportunities we are facing, so we are very sorry to see him leave,” she said.

“Ruairí’s insight and expertise even in the short time he was here, was invaluable to me and the Board and I thank him and wish him well.”

It was reported in September by the Irish Times that among the options being considered by NatWest as part of the strategic review is a wind down of its operations in the Republic, as well as possible sale or merger with another institution.

It is understood that Mr O’Flynn was aware that the review was taking place prior to his appointment.

“Ruairí has asked me to reassure you that his decision to resign is personal and not linked to the ongoing strategic review,” Ms Howard said.

“He also asked me to thank you all for your continued hard work and dedication to serving our customers well.”

Mr O’Flynn’s resignation is immediate.

Another non-executive director, Martin Murphy, who is the former boss of Hewlett Packard in Ireland, will take over the role of Chairman on a temporary basis.