The board of directors of Irish Nationwide Building Society says it has accepted with regret the resignation of Dr Michael Walsh as chairman.
Dr Walsh has informed the board that there are 'no commercial issues' that would have impacted on his decision.
In a statement the board said it 'understands and fully accepts that he can no longer devote the increasing amount of time required to provide the necessary oversight and leadership in the current challenging times for all financial institutions'.
Mr Walsh had been chairman since 2001. The board said Terence J Cooney will be acting chairman until a successor is appointed.
Irish Nationwide is expected to hold a board meeting either today or tomorrow following the unexpected resignation of Dr Walsh.
The society has been at the centre of questionable loan arrangements involving the former chairman of the now nationalised Anglo Irish Bank.
Senator Dan Boyle of the Green Party said Irish Nationwide was the institution that facilitated the movement of director loans from Anglo Irish.
He also said these practices must have been known within Irish Nationwide at some level.
