Australian banks increased their commercial property exposures by more than $4.7 billion in the September quarter to $240 billion, despite repeated warnings from the Reserve Bank of Australia surrounding rising risks in the sector.

Exposures in office accommodation, where there are still high vacancy rates but increasing prices, rose $1.4 billion to $71.9 billion. It was the biggest increase since the March quarter and follows comments made earlier this month from the RBA assistant governor Malcolm Edey about the continued ­divergence between prices and rents.