A teenager threatened a 70-year-old man with a gun in an attempt to steal his van, adding to Victoria's escalating number of carjackings.

On October 21, the 70-year-old was sitting in his parked van on Dalton Road in Lalor when a powder blue Ford Falcon with no registration plates pulled in front of him, police said.

Police want to speak to this young man over an attempted carjacking in Lalor.

The Ford driver got out of his vehicle and approached the victim, pulled out a black handgun and demanded he get out.

The 70-year-old lay down in his van to protect himself, and the young offender walked back to his car and drove off. He was last seen travelling east on Childs Road in Lalor.