Ulster Bank has confirmed that it will close up to 39 branches on the island of Ireland, in an effort to return the group to profit by 2016.
The bank said it would cut its branch network from 214 to between 175 and 185 but did not give a breakdown of where the closures would occur.
In a presentation to investors, the bank said its plans would "significantly" reduce its workforce, from around 5,800 full-time staff to between 4,000 and 4,500 by 2016.
Ulster Bank's chief executive Jim Brown said that the bank is "well on the way to delivering a good, profitable bank but clearly it will be smaller than it was at the peak of the boom".
Mr Brown said that the bank was "holding revenue, improving margins" and seeing costs continue to come down. He also said loan impairments were "improving".
In January, Ulster Bank confirmed its intention to close five branches and six sub-offices in the Republic of Ireland by May. Another seven branches and four sub-offices in Northern Ireland were closed in June.
IBOA's general secretary Larry Broderick has responded angrily to the surprise revelation by Ulster Bank that it wants to close more branches.
The finance union leader said the bank’s announcement had come as a bolt from the blue - without prior consultation with employees or negotiation with the union.
Ulster Bank has 1.3 million customers in the Republic of Ireland, while it has 135 branches here. It has another 718,000 customers in the North with 79 branches there.
Media to blame for some mortgage arrears - Brown
Jim Brown also blamed coverage of debt forgiveness in the media for adding to the number of people who were deliberately not paying their mortgages.
Mr Brown said that Ulster Bank was experiencing cases of strategic defaults among mortgage borrowers.
He added: "We are seeing cases of those who can pay but who won't pay."
The bank also said 35% of those who are in arrears of 90 days or more were not making any payments on their mortgages.
The lender said those borrowers would be going into the "legal system".