Members of the Financial Services Union (FSU) in AIB have voted overwhelmingly to reject new hybrid working principles proposed by the bank.
The FSU said it will now refer the issue to the Workplace Relations Commission (WRC) for conciliation.
The union added that it remains open to ongoing engagement with AIB.
In July, AIB said that staff would be required to work in an office-based location for a minimum of three days a week.
At the time, the FSU accused the bank of acting unilaterally and described the announcement as regressive, shortsighted and without justification.
Following negotiations between the two sides, AIB presented the FSU with new proposals including usage of AIB hubs, reviews of pre-existing arrangements, and a commitment to agree any future changed with the union.
Those proposals have now been rejected in a ballot of FSU members.
"The FSU want to find a solution that works for staff and the employer," said General Secretary of the Financial Services Union John O'Connell.
"We believe it is possible to agree new hybrid working principles that addresses the concerns of both employees and the employer."
"We have referred the matter to the WRC but will make ourselves available to meet with AIB management to work towards resolving the issue," Mr O’Connell said.
AIB said it engaged extensively with the Financial Services Union and as a result of those discussions it drafted the hybrid working principles.
"We will continue to engage with our people on our updated hybrid working arrangements, which will come into effect as planned on 1 January, while also continuing to engage with the FSU using our normal industrial relations process," an AIB spokesperson said.
