The Ulster Bank is facing more than 1,500 legal actions in Northern Ireland and the Republic in a row over new contracts with its staff.
Finance union IBOA said it was ready to take on the bank over its refusal to honour what the union believes to be its contractual obligations to staff.
Ulster Bank has refused to comment but it is understood it intends to contest any legal action brought by the union.
"We are now awaiting dates from the Rights Commissioner in the Republic and the High Court in Belfast," IBOA senior industrial officer Steve Tweed said. The union claims that staff who refused to sign inferior contracts -- that significantly changed pay and conditions -- were denied payments they were entitled to.
A fifth of 5,000 bank officials have refused to sign such contracts and it is on behalf of this group that the actions on both sides of the Border are being taken. One of the disputed payments concerns an annual allowance paid to staff since RBS acquired the bank, which is equivalent to 10pc of salary and is usually made at the end of the year.
IBOA claims that those who did not sign the new contracts were told they were not entitled to that payment.
A second disputed payment relates to performance-related pay, and the union again claims that those who refused to sign the new contracts were also denied this payment.
In the Republic, the union's case for the payment of contractual obligations will be heard by the Rights Commissioner service.