Lending to business went into reverse in October, with the latest Reserve Bank data showing a fall in the value of lenders' business loan portfolios for the first time since early 2017.Aggregate business loan portfolios fell by 0.1 per cent in October, compared with the previous month. They grew by 2.7 per cent over the 12 months to October - the lowest annual growth rate since 2014.Housing finance growth continued to be weak. Aggregate mortgage balances grew by 0.3 per cent in October and by 3 per cent over the past 12 months.Owner-occupier balances were up 0.4 per cent month-on-month and by 4.8 per cent over 12 months. Investor loan balances were flat month-on-month and down 0.2 per cent over 12 months.APRA figures show that, with the exception of Commonwealth Bank, the big banks are struggling to make headway in a highly competitive market.ANZ recorded growth of 0.1 per cent in October, after suffering a net outflow of mortgage business over the past six months.Commonwealth Bank grew ahead of system in October, with a 0.5 per cent increase in the value of its mortgage book. It is a little below system over 12 months, with growth at 2.5 per cent.NAB's mortgage book was flat in October and flat over 12 months.The value of Westpac's book fell 0.6 per cent in October and fell 0.7 per cent over the past 12 months.