The Housing Industry Association's housing affordability index, which measures the capacity of households to service mortgages, shows Sydneysiders must fork out $4,729 per month, or nearly $57,000 a year, to service a standard mortgage on an averaged-priced home in the city.

That is more than 30 per cent of the earnings of a Sydney household with two average full-time wages - the portion of income widely accepted to be a manageable housing repayment.

"House buyers in Sydney now require more than double the average income in Sydney to be able to afford the averaged-priced house in that market," the report said.

"This quarter's result is a further widening of the affordability gap between Sydney and everywhere else. It has the lowest affordability in the country by a large margin."

The association's affordability index for Sydney dipped to an all-time low of 48.7 in the June quarter.

"These are concerning figures," said HIA principal economist Tim Reardon.

The findings come as opinion polls show an unprecedented level of public anxiety about the cost of housing in the wake of a Sydney property boom that has lasted nearly five years.

The quarterly Ipsos Issues Monitor, which asks respondents to select the three most important issues facing their state, shows housing now tops the list of concerns in NSW.

It found 47 per cent of NSW respondents identified housing as an important issue facing the state in the June quarter, just shy of the record 50 per cent in the previous survey. That is compared with 29 per cent in 2013.

David Elliott, head of the Ipsos social research institute in NSW, said housing was the "clear No. 1 issue" that people in NSW felt their state was facing. "The results [for housing] in 2017 are the highest we've seen in the last 10 years," he said. "The increased concern is not overly surprising as housing affordability and availability seems to be one of the hot topics in the community and in the media. Perhaps this growing concern is reflecting a desire to hear from government and how they plan to tackle the issue."The combination of soaring property prices and sluggish wage growth has contributed to the decline in housing affordability. This deterioration has occurred despite record low interest rates.

Two years ago, it took 1.75 average full-time wages to affordably service a standard loan on an average-priced Sydney home, but that has reached 2.06 average full-time wages, the association's affordability report said. In the rest of NSW, it takes 1.39 full-time wages to service a standard loan on a median-priced home.

Melbourne was the least affordable city after Sydney. It takes 1.64 average full-time wages to affordably service a standard loan on a typical house in Melbourne.

Nationally, the affordability index showed a deterioration of 0.3 per cent in the June quarter and by 2.2 per cent over the year.

The association's previous report, released in April, put Sydney's affordability multiple at 1.74 full-time wages in the March quarter but that was revised up to 2.04 in the latest report, with the June quarter multiple reaching 2.06 full-time wages. It was the first time the report has shown an affordability multiple over two full-time wages.