A P-plate driver has allegedly been caught drunk behind the wheel with a little girl in the backseat.

The 26-year-old was stopped on Sydney's north shore for a random breath test about 2.05am (AEST) on Sunday.

A five-year-old girl was in the backseat of the car, travelling on the Pacific Highway at Wahroonga.

The driver allegedly returned a positive result and was taken to a local police station, where she recorded a reading of 0.182.

She's been issued a court attendance notice for high range drink-driving and is due to appear in Hornsby Local Court on September 5.

Her licence was also suspended, police said.