A Liberal volunteer was allegedly injured with a corkscrew on Friday night by a man at a polling station in the hotly contested electorate of Warringah, where former prime minister Tony Abbott is facing off against independent Zali Steggall in a race that has turned increasingly bitter.

A number of Liberal volunteers were putting up campaign material at Balgowlah Heights Public School when a 62-year-old man allegedly started yelling abuse at the volunteers, police said.

"The man then thrust a corkscrew at the stomach of a 31-year-old man, causing a minor injury," police said in a statement. "He then started ripping down the banners that had been erected, before fleeing the scene."

Police and ambulance officers attended the scene. The 31-year-old victim, a campaign volunteer, was treated at the scene and did not require hospitalisation.