The homicide squad is investigating the discovery of a dead man and woman inside a car in Melbourne's outer north-west.

The bodies were discovered on Taylors Road in Plumpton, with police called to the scene shortly before 11.30am on Thursday.

The car where the bodies of a man and woman were discovered at Plumpton. Credit:Luis Ascui

A council worker noticed a man slumped in the front of the silver 1999 Ford Falcon sedan. The man had a gunshot wound to the upper body and a rifle or shotgun was found nearby.

The woman's body was found lying across the back seat of the car soon after.