Australian economists are forecasting another interest rate hike from the Reserve Bank of Australia (RBA) this month, with a further increase potentially following soon after, piling more pressure on mortgage holders. The fourth rise of the year is expected at the RBA's 28–29 September board meeting, taking the cash rate from 4.35 per cent to 4.60 per cent, with markets pricing a strong chance of a further hike in November as the central bank battles persistent inflation.

Analysts put the probability of the September increase at 76 per cent, and Westpac says a November rise is now fully priced in by markets. Canstar calculates that a borrower with a $600,000 mortgage would pay $92 more a month for each hike, rising to $184 if both occur; a $750,000 loan would cost $230 more, and a $1million mortgage an extra $306 a month. Westpac economists point to rising petrol prices, up since the government ended fuel excise cuts, as inflating spending figures, while RBA deputy governor Andrew Hauser warned the bank would act sharply and without delay if needed to bring inflation under control.