22 organisations have issued a stark warning saying that Sydney’s smoky air has become a public health emergency.

The groups are calling for urgent government action, as a blaze three times the size of Stewart Island burnsg north of Sydney, continuing to blanket the city in a haze of smoke.

John Bonning, President of the Australasian College for Emergency Medicine, says it's a significant danger for people with respiratory illnesses.

He told Andrew Dickens those include asthma, emphysema, allergies, those with cardiac conditions, the very old and the very young.

He says there will be ongoing risk and harm and there's data to suggest there's an increase in premature births.

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