* Aussie shares mostly unchanged as materials weigh
* Banks trade in tight range ahead of inquiry's interim report
* NZ falls on consumer staples and utilities
By Aditya Soni
Sept 27 (Reuters) - Australian shares treaded water on Thursday as materials stocks fell on lower copper prices and banks drifted sideways ahead of an interim report due on Friday from a powerful inquiry into the financial services sector.
The S&P/ASX 200 index .AXJO fell 0.1 percent or 7.20 points to 6,185.10 by 0200 GMT. It rose 0.1 percent on Wednesday.
Materials, especially mining stocks, dominated the losses, hurt by sustained weakness in copper prices.
Copper was on track for fourth straight day of losses on Thursday after falling 0.6 percent in the previous session.
Escalating Sino-U.S. trade tensions have pushed the industrial metal 13.4 percent lower in 2018.
Global miner BHP BHP.AX dropped as much as 1.2 percent and was the biggest drag on the benchmark, while Rio Tinto (LON:RIO) Ltd RIO.AX dipped 0.8 percent.
Energy stocks were also in red, falling 0.4 percent after three sessions of big gains.
Woodside Petroleum Ltd WPL.AX , the biggest listed oil and gas explorer, fell 0.3 percent, while Oil Search Ltd OSH.AX fell 1 percent.
Meanwhile, banks drifted sideways ahead of a high-profile inquiry's interim report due on Friday.
The Royal Commission, as the powerful inquiry is called, has already revealed widespread wrongdoing in Australian financial services, making it the worst-performing ASX sector this year.
The inquiry questioned on Wednesday whether the insurance industry's system of self-regulation should be overhauled amid evidence of widespread misconduct. Rodda, market analyst at IG Markets, said the falls in banks and insurance stocks were being driven by speculation around the Royal Commission report.
Index heavyweight Australia and New Zealand Banking Group Ltd ANZ.AX fell as much 0.5 percent to its lowest since July 3, while National Australia Bank Ltd NAB.AX dipped 0.2 percent.
Across the Tasman Sea, shares of consumer staples and utilities sent New Zealand's benchmark S&P/NZX 50 index .NZ50 0.5 percent or 50.04 points to 9,299.81, its lowest in more than a week.
A2 Milk Company Ltd ATM.NZ fell as much as 2.5 percent to a more than two-week low and was the biggest drag on the benchmark, while Meridian Energy Ltd MEL.NZ fell 3.2 percent to its lowest since Sept. 12.
Earlier in the day, New Zealand's central bank kept its cash rate steady at a record low on Thursday and said the direction of the next change was still in the balance, citing tepid inflation and a turbulent international outlook.