Suncorp Bank suffered some deterioration in the asset quality of its core bank during the March quarter.After reporting bad debt charges of A$7 million in the September 2011 quarter, and $2 million in the December quarter, the charge jumped to $13 million in March 2012. The March quarter impairment loss was 24 basis points of credit risk-weighted assets (annualised).The bank said the increase was largely the result of an increase in the collective provision charge. "This reflects the uptick in arrears and the outcome of regular reviews of collective provision factors for smaller exposures," it said.Impaired assets rose from $148 million in September and $141 million in December to $220 million in March.The bank said: "The increase predominantly relates to two mid-sized business lending exposures. The housing loan portfolio contributed $12 million to the increase in impaired assets."Past due loans not shown as impaired increased by 11 per cent in the quarter. Home loans 90 days past due rose from 72 basis points of the home loan book at December to 82 basis points in March.Credit risk-weighted assets in the core bank increased from $21.3 billion in the December quarter to $21.8 billion in the March quarter - a 2.7 per cent increase. Home lending increased 3.3 per cent during the quarter.The ratio of deposits to loans was 69.8 per cent - close to the top of the bank's target range.