The progressive has seen its profits increase
Northern Ireland's Progressive Building Society has seen its pre-tax profits drop by £5m over the last year.
The society published its results for 2008, which shows gross receipts are up by 17% to £418m, and total assets have increased by more than 10% to £1.6bn.
However, pre-tax profits were £4m, compared to £9m in 2007.
The society has set aside £900,000 for possible bad debts and said it was angry at having to help bail out "reckless" lenders.
The Progressive has to contribute to the Financial Services Compensation Scheme towards the bail-out of Bradford & Bingley Bank.
The total cost to the Progressive is likely to be more than £2.2m over three years.
Darina Armstrong, Progressive's finance director, said prudent societies were being penalised.
"We share the anger of many of our members that our cautious and prudent management of the society's affairs over the years has resulted in the society being financially penalised due to the recklessness of some elements of the banking sector," she said.
"Building societies maintain higher ratios of savers' funds on their balance sheets than most banks and will pay a disproportionately high contribution towards the financing of the rescue."
Born out of the merger of five small societies the Progressive Building Society first opened its doors under the "Progressive" name in 1914 and has 11 branches in Northern Ireland.