Driver drags officer 20m at traffic stop

A man has been charged after a police officer was allegedly dragged 20 metres by a car in Sydney.

The drama unfolded after police stopped a sedan in Monfarville Street, St Marys, in western Sydney, about 6.30pm on Friday and arrested the male driver.

As they were speaking to the driver, the passenger in the car allegedly got into the driver's seat and drove off.

An officer attempted to stop the car and was dragged 20m. He sustained grazing and bruising to his left arm and leg but did not need medical attention.

The car was recovered a short time later in a nearby street.

About 11.40pm, a 21-year-old man turned himself in to officers at St Marys Police Station.

He was arrested and charged with using an offensive weapon to avoid detention, and drive while disqualified.

He was refused bail to appear in Parramatta Bail Court on Saturday.