New lending to residential property investors has fallen for five straight months, with the latest data showing the rate of decline accelerating.According to the latest Australian Bureau of Statistics housing finance data, the value of new mortgage lending to investors fell 8.5 per cent in September, compared with the previous month (in seasonally adjusted terms).The month-on-month fall of 8.5 per cent is the biggest fall so far this year. Meanwhile new lending to owner-occupiers continued to grow strongly - up three per cent, compared with the previous month.Overall, total new housing finance commitments were down 1.6 per cent in September, compared with the previous month.Lenders settled A$33.4 billion of mortgages in September - 12.4 per cent more than the same time last year.The average loan size was $379,400, compared with $371,000 the previous month and $328,700 a year earlier.First-home buyers made up 15.4 per cent of the market.Earlier this month the Reserve Bank reported that lenders' investor mortgage balances grew by 0.5 per cent in September, compared with the previous month, and by 10.4 per cent over the 12 months to August.