AN UNHERALDED State Government concession changing the rules on how much public transport must be nearby for developments to be approved could open the way for strips of high-rise flats, councils have warned.

Rules on affordable housing construction were quietly changed last September while Premier Kristina Keneally was planning minister so blocks of flats could be built within 400m of a bus stop which had services running from 6am to 6pm Monday to Friday only.

Previously the requirement had been a need for bus services to run from 6am to 9pm seven days a week.

The Western Sydney Regional Organisation of Councils warned yesterday the change meant high-rise could now occur in "nearly any Sydney residential street".

More developments can now be made in less-serviced outer suburban areas such as Windsor and Picton. Under the rules, only 10-20 per cent has to be "affordable".

Holroyd mayor John Perry said his council already had three development applications before it using the new rules. "The problem we have is the location of them - they're not near the major transport corridors," he said.

Western Sydney Regional Organisation of Councils president Allison McLaren said the changes meant even quiet low density areas with few bus services were "now vulnerable to large scale high density developments".

"The first our councils knew of it was when developers started showing up with applications to build high density apartments in areas that would not have met the former criteria," she said.

"It was only when planning officers looked up the SEPP to confirm the terms they discovered this change had gone through last September."

Ms McLaren accused the Government of "unfair and sneaky conduct", and said it opened "all of Sydney up to random and ill-conceived high density development".

But a spokesman for the Planning Minister Tony Kelly accused Ms McLaren of "ill-informed scaremongering", and said the changes would increase the supply of affordable housing which would drive down housing prices.

Originally published as Kristina Keneally's flat plague