Sydney's housing market has been ranked the least affordable city in the world for the second year running, posing a threat to 'living standards'.

A global report assessing the affordability of middle-income housing ranked Sydney 93rd out of 94 metropolitan markets.

The 2023 Demographia International Housing Affordability Report, released on Monday, ranked Sydney second only to Hong Kong, the world's least affordable country.

Sydney retained its place in the 2022 report after falling from the third least affordable market in 2021, with the report showing house prices increasing at six times the rate of inflation.

"There is a widely held view that deteriorating housing affordability is an existential threat to the middle class," said author Wendell Cox from the Institute for Urban Reform.

"Housing affordability in 2022 continues to reflect the huge price rises that occurred during the pandemic demand shock.

"Some improvements in housing affordability have occurred since then, with more likely as demand shocks are expected to be replaced by more normal market trends."

The latest report, for the September 2022 quarter, ranks markets in Australia, Canada, China, Ireland, New Zealand, Singapore, the UK and the US based on the relationship between income and house prices.

"Sydney is the least affordable market with a median multiple of 13.3, making it the second least affordable market internationally," according to the report.

"The Australian market has a median of 8.2, up from 6.9 in 2019," the report said.

"This equates to an increase in median household income of 1.3 years.

"All five of Australia's major housing markets have been severely unaffordable since the early 2000s."

Australia's other major cities also ranked highly in the list of least affordable housing markets, with Melbourne ranking 9th, Adelaide 14th and Brisbane 15th. perth came in at 50th.

"Australia's major housing markets have experienced particularly significant housing affordability losses," the report said.

"Median house prices in Adelaide have increased by 6.1 times the rate of inflation, as measured by the Consumer Price Index (CPI), since 2020.

Measured by the Consumer Price Index (CPI).

"Sydney house prices have increased by 6.0 times CPI, Brisbane by 5.2 times, Melbourne by 4.9 times and Perth by 4.2 times.

"In each of these five housing markets, house price inflation since 2000 has exceeded all product groups that make up the CPI."

The report noted that affordability issues could see a decline in "living standards".

"As pandemics and blockades continue into another year, households move from dense urban communities to larger ones.

As the pandemic and embargo continued into another year, households continued to move from dense urban communities to larger homes, often with large yards (gardens) in suburban and remote areas," the report said.

"The result has been to drive up prices in many markets at an unprecedented rate. As a result, many low- and middle-income households are already suffering the worst consequences of housing inflation and their living standards will fall further."