The Irish Bank Officials Association (IBOA) is threatening AIB's First Trust with industrial action over a decision to close four branches in Northern Ireland.
The union's general secretary, Mr Larry Broderick, said the decision "flies in the face" of negotiations to conclude a partnership agreement between the two parties. Unless the bank defers the closures, he said, "we will be left with no alternative but to ballot members on an appropriate course of action".
However, a spokesman for the bank said the closures were part of a service delivery review announced in 2001, which was unrelated to the "ongoing negotiations" on a partnership deal.
He added the union had been informed in early December of the planned Belfast closures at Dunmurry, Shankill Road, Strandtown and Queen's Island.
The bank confirmed to customers earlier this week that the four branches would shut down in April. This follows a number of other closures in Armagh and Omagh, among other locations, reducing the number of First Trust outlets in the North to 60.
The group, which was formed in 1993 by the merger of AIB and Trustee Savings Bank in Northern Ireland, employs about 1,500 people. It says the restructuring programme, which includes a £13 million sterling (€19 million) investment in building and refurbishment projects, will result in no job losses, with staff transferring to nearby locations.
But Mr Broderick said the closures were "unacceptable from both a staff and customer point of view", and would deprive the community in each area of its local bank branch.
"This development is extremely disappointing and is at variance with the partnership principles between the IBOA and First Trust Bank," he added.
The trade union is seeking a three-year deal with the bank on similar terms to that agreed with its parent company last April. Demands include salary increases for customer service officials, the same 35-hour week as exists in AIB in the Republic, and the application of long- service increments for staff.
