Members of Newbridge Credit Union in Co. Kildare say plans to merge the branches "will have a devastating impact" on small businesses.
Over 100 people are due to demonstrate outside the Central Bank today, calling for more information on the planned merger with the Naas branch.
More than 37,000 people are members of Newbridge branch, making it one of the largest Credit Unions in the country.
The Central Bank has moved to reassure members of Newbridge Credit Union that there are no plans to shut the branch.
A spokesperson for the Central Bank says that even if the merger goes ahead, there is no question either branch will close.