National Irish Bank has reported a pre-tax loss of 400 million euro (£348.3 million) for the first six months of the year.
The bank, owned by Danske Bank Group, set aside 420 million euro (£365.7 million) to handle bad loans leading to the pre-tax loss.
Commercial property loans amounted to 3.3 billion euro (£2.9 billion), with most of the bank's loan impairment charges in this area.
National Irish Bank chief executive Andrew Healy said performance was broadly in line with expectations and reflected the "harsh economic conditions that continue to prevail".
"While our restructuring programme is delivering benefits to the cost line, impairments remain frustratingly high and are caused in the main by the continued decline in property values," he said.
"Our parent, Danske Bank Group, remains strongly committed to Ireland and to National Irish Bank.
"We believe the changes we have made to our business create a good platform for growth once conditions improve."
The bank's total loan book was 9.1 billion euro (£7.9 billion), down 9% on last year.
Customer deposits increased by 21% to 5.1 billion euro (£4.4 billion).
The bank reported an operating profit before impairment charges of 20 million euro (£17.4 million), a drop of 22%.
Income fell 19% to 68 million euro (£59.2 million) due to reduced customer demand and the impact of the impaired loans.
Costs fell by 18% to 48 million euro (£41.8 million), largely driven by the bank's restructuring programme.
Danske Bank Group reported a profit before tax of 480 million euro (£418 million), up 14% on the first half of 2010.