Northern Bank has reported a loss of £49.7m for the first three quarters of 2010, compared to a £102m loss in the same period last year.
Although its operating profit increased to £39.6m, that was wiped out by £89.4m set aside to cover bad loans.
Its parent company, Danske Bank Group, announced pre-tax profits of £301m.
The bank's chief executive Gerry Mallon said that he was pleased with the core performance of the business in the "fragile economic environment".
Mr Mallon said conditions in the economy and particularly in the property and construction sector, were likely to remain difficult for some time.
"The property and construction sector has been depressed for some time," he said.
"The question now is when are we going to see some sign that confidence is returning to the property market.
"I think we have to accept that cutbacks in public sector spending will take its toll. What we need now is some certainty about what the impact of those cuts is going to be."
Danske's unit in the Irish Republic, National Irish Bank (NIB), made a pre-tax loss of 468m euros (£405m) in the first nine months of this year.
The bank said it had put €504m (£437m) aside for provisions for bad debts. This is €40m (£34.6m)less than the same time last year.
It said its operating profits, before charges for impaired loans, for the nine-month period were down 25% to €36m (£31.2m).
The bank said that income in the nine month period was down 11% to €124m due to reduced customer demand, the impact of impaired loans and lower deposit margins.
Northern Bank began in 1809 as a Belfast-based banking company known as the Northern Banking Partnership.
It was acquired by the Danske Bank Group in 2005, the largest bank in Denmark and a major player in Scandinavian financial markets.
It has 83 branches in Northern Ireland employing 1250 people.