A teenager remains in a serious condition after he was hit by a 92-year-old Victorian driver who mistook his accelerator for a brake.

The elderly man ploughed into three pedestrians when he was trying to park his car in Portarlington on Saturday morning.

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He pressed the accelerator instead of the brake and the car then hit three people after mounting the kerb, police say.

A 16-year-old boy was flown to the Royal Melbourne Hospital with head injures, Ambulance Victoria spokesman John Mullen said.

He remained in a serious but stable condition on Saturday night.

A 19-year-old man and a man in his 60s received minor leg injuries.

The driver, a Portarlington man, was unharmed and is helping police.