Dual income households are putting a bigger slice of their monthly wages into mortgage repayments.
Australian households with two income earners needed 28.7 per cent of their monthly salary to meet monthly mortgage repayments in September, up from 27.4 per cent in the same month a year earlier, credit ratings agency Moody's said.
Moody's senior analyst Alena Chen said housing affordability had declined across the country, despite varied trends in major cities.
Sydney, Perth and Adelaide had seen an improvement in affordability, while it worsened in Melbourne and Brisbane, she said.
"We believe housing market imbalances and the large build up of household debt continue to pose risks to the performance of Australian residential mortgage-backed securities," Ms Chen said.
Moody's said household debt as a percentage of household disposable income is at a record high of 193.7 per cent.
Sydney remains the most unaffordable city in Australia, even though its market has cooled since regulatory measures were introduced to curb new interest only loans and housing investment loans.
Moody's said the long term effectiveness of the measures remains to be seen, as prices in other cities, such as Melbourne, continue to rise.
The Reserve Bank of Australia remains concerned about property prices, saying at its October board meeting that housing debt was still outpacing the slow growth in household incomes.