Danske Bank Ireland, formerly National Irish Bank, is closing with the loss of 150 jobs in the Republic.
Larry Broderick, the head of the IBOA trade union, said the job losses at the bank would be compulsory.
"We are shocked at the decision and the lack of consultation with staff and customers. We would ask the bank to reconsider," he stated.
Danske is the second bank in Ireland to close in the space of a week after ACC announced it is handing back its banking licence.
In a statement, Danske Bank announced organisational changes to its Irish operations, saying that day to day personal customer products and services will be withdrawn on a phased basis during the first six months of next year.
The bank said that after a detailed review of its Irish operations, the sale of personal and business banking products to new customers will be discontinued with immediate effect.
Danske also said that it will now start talks with the banking unions in relation to the impact of the changes on its staff numbers.
In a statement, the bank said the decision was reached because of the difficult economic and trading environment, where the bank has failed to re-establish a sustainable retail banking business. Danske said that from now on it would focus the Irish business towards corporate and institutional clients. The bank assured customers today that their deposits will be repaid in full. It said it will write to all customers in the coming weeks to clarify the impact on the changes. Danske Bank Ireland also announced a loss before tax of E31.4m for the first nine months of 2013, while it also recorded impairment charges of E22.8m. "The decision regarding the personal and business banking divisions is necessary to stem the losses that continue to accrue in those units. Against the backdrop of the difficult economic and trading environment in Ireland, the bank has been unable to re-establish a sustainable retail banking business model," commented Gerry Mallon, Head of Danske Bank UK and Ireland in an RTE News report.