Meetings between Ulster Bank and the Financial Services Union (FSU) have been described as "difficult and deeply troubling" as the threat of closures or carving-up the bank looms.
According to the union's general secretary, John O'Connell, Ulster Bank's CEO, Jane Howard, refused to answer "any questions about the strategic review or to adequately respond to recent media reports about possible talks between NatWest and [Permanent TSB]".
In a statement following today's meeting, Mr O'Connell said he conveyed staff worries regarding the uncertainty to Ms Howard, saying he left the CEO "under no doubt as to the level of anxiety and stress that bank staff are under".
"The situation is now very serious. The threat of a closure or carve-up of the bank is growing, and this will seriously impact communities, customers, staff, and businesses all over Ireland.
"The manner in which people have been treated here is totally unacceptable. This union will not stand by while loyal staff are treated so poorly. Their loyalty, commitment and well-being need to be central to the review process," Mr O'Connell said.
He claimed staff were being asked to "undertake work in respect of the process that could enable the sale or carve-up of Ulster Bank", adding the bank was "asking them to sign non-disclosure agreements, so they cannot discuss it".
"The FSU clearly stated in the meeting that a carve-up of the bank’s assets is not an acceptable outcome and under no circumstances should a vulture fund be able to get its hands on any part of the loan book.
"If NatWest decides to exit the Irish market, any solution needs to involve the maximum protection for customers, for jobs and the branch structure," Mr O'Connell said.
The union said action is needed now, calling on the Minister for Finance and the Central Bank to make an urgent statement, as a decision regarding the future of Ulster Bank is "coming fast" and it "cannot be allowed to slip under the radar",