The annual housing affordability study from Demographia ranked Sydney the second-least affordable city behind Hong Kong, with Vancouver rounding out the top three. 

Melbourne and Adelaide didn’t fare much better, placing at number seven and number nine. 

Brisbane and Perth also ranked in the least affordable 25 per cent of the 94 cities observed. 

The report focuses on the ability of middle-income buyers to purchase homes and examines data from housing markets across the English-speaking world. 

Housing markets from Australia, Canada, Hong Kong, Ireland, New Zealand, Singapore, the United Kingdom and the United States were surveyed to put together the list. 

The top three most affordable cities were Pittsburgh, Rochester and St Louis, with nine of the top ten cities located in the United States. 

The report said an indicator of a strong middle class had long been the ability to own a home, with limited housing affordability threatening to eliminate the middle class.

"Affordability is disappearing in high-income nations as housing costs now far outpace income growth," the study said.

"The crisis stems principally from land use policies that artificially restrict housing supply, driving up land prices and making home ownership unattainable for many."