Sydney's cleanest beaches downgraded - Yahoo!7 News

AAP Some of Sydney's prime swimming spots have had their water quality ratings downgraded.

Formerly top-ranking Sydney beaches have seen their water quality drop over the past 12 months, an environmental report says.

The latest State of the Beaches report has been released and reveals 81 per cent of swimming locations reviewed in NSW have reached very good or good gradings.

The top gradings indicate the sites are suitable for swimming most or almost all of the time.

Among the best swimming spots in Sydney are Palm Beach, Whale Beach and Avalon on the Northern Beaches.

But neighbouring beaches Dee Why, South Curl Curl and Mona Vale have all been downgraded from the very good rating they secured last year to good.

The report states while Dee Why is suitable for swimming most of the time the water is susceptible to pollution from several sources of faecal contamination, including stormwater.

South Curl Curl and Mona Vale are also susceptible to pollution following rainfall.

Sydney Water is amplifying pipes and pumps and incorporating storage tanks in the sewerage system in an attempt to reduce wet weather sewage overflows between Narrabeen and Manly.

Boat Harbour near Cronulla was rated poor this year for the first time.

Eight Sydney beaches are rated as very good, which is down from 15 last year. The report links major rainfall events over the last couple of years as a major driver of pollution to recreational waters.

An eastern suburbs beach formerly on the poor list has managed to climb the ranks and secure a good grading after a $3 million effort to improve water quality.

A stormwater drain was the cause of contamination at Malabar Beach.

Last year the stormwater was diverted further offshore and according to the report, the beach's water quality has improved substantially.

Six ocean beaches impacted by contamination - including discharge from lagoons and estuaries - were graded as poor including Kilick Beach at Crescent Head and Terrigal Beach on the Central Coast.

The NSW opposition says the state is returning to the "bad old days" when overflows made it unsafe to swim at beaches.

It attributed the drop in water quality at some Sydney beaches to a reduction in Sydney Water's budget and workforce, outsourcing of mechanical and electrical workers and a record number of bypasses at wastewater treatment plants.

"After 15 years of improvement by previous Labor governments, the O'Farrell government is overseeing an increase in pollution and sewage on our beaches," opposition water spokesman Walt Secord said.

"We are returning to the bad old days when it was unsafe to swim on the beaches due to overflows.

"The O'Farrell government cannot blame rain as NSW has experienced its warmest January to September period on record. NSW has had its mildest winter in more than 150 years."