The number of delinquent housing loans underlying Australian prime residential mortgage-backed securities increased to 1.21 per cent in April from 1.16 per cent a month earlier, according to a recent report by S&P Global Ratings. "Part of the increase reflects a decline in outstanding loan balances, but we believe interest-rate rises announced by different lenders during the past few months affected the [Standard & Poor's Performance Index] for Australian prime mortgages, given that most of the loans are variable-rate mortgages," said S&P's analysts.New South Wales, Victoria, and Queensland, which account for around 80 per cent of total loan balances, all recorded increases in arrears during the month. Queensland recorded the nation's largest increase, with arrears increasing to 1.66 per cent from 1.58 per cent in March, followed by New South Wales, where arrears rose to 0.91 per cent from 0.85 per cent a month earlier. Regional banks recorded the greatest increase in arrears among all loan originators, with mortgage repayments more than 30 days late increasing to 2.27 per cent in April from 2.02 per cent in March. "We attribute this in part to a decline in outstanding loan balances and the regional banks' greater exposure to Queensland; around half of all regional banks' outstanding loan balances are domiciled in the state," S&P said.Nonconforming arrears fell to 5.03 per cent in April from 6.17 per cent a month earlier, against a backdrop of increasing loan balances. Mortgage repayments more than 90 days past due made up around 41 per cent of the total nonconforming arrears in April compared with 60 per cent for prime arrears.