The impairment of a large corporate loan contributed to a 24.1 per cent fall in HSBC Bank Australia's profits last year. A financial report filed with the Australian Securities and Investments Commission shows the bank's net profits fell from A$177.2 million in 2011 to $134.5 million last year.Loan impairment charges jumped from $53.3 million, in 2011, to $135 million last year.Another contributor to the bank's fall in earnings was a 10.6 per cent increase in operating expenses.Net interest income rose 3.6 per cent to $606 million, and net fee and commission income rose 15.7 per cent to $197.8 million.According to the directors' report, the growth in fee income came from increased credit card activity and trade activities. According to Australian Prudential Regulation Authority figures, HSBC card balances grew by 11 per cent last year.Its mortgage book grew by 4.5 per cent, which was a little ahead of system growth.Total assets were $24.6 billion - up 2.5 per cent from 2011.The bank's tier one capital ratio at December 31 was 8.93 per cent and its total capital ratio was 11.33 per cent.