Charges have now been laid after a polling booth punch-up left an elderly man seriously injured ahead of the federal election.

The chaotic scene erupted outside a Sydney polling booth after a teenager allegedly hit an elderly man at Ashfield Town Hall on Liverpool Rd in Ashfield about 1pm on Wednesday, NSW Police said.

WATCH THE VIDEO ABOVE: Pothing booth punch causes serious injury.

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A 79-year-old man was treated at the scene before being rushed to Royal Prince Alfred Hospital in a serious condition.

A 17-year-old teenager was arrested at the scene, and taken to Burwood Police Station.

Witnesses told 7NEWS the man, wearing a MAGA (Make America Great Again) hat, was about to deface one of the many Anthony Albanese election posters when a female volunteer confronted him and began filming.

It is understood the teenager thought the woman was in danger and stepped in, striking the man from behind and causing him to fall to the ground.

There’s no indication the teenager is connected to any political group.

He has since been charged with assault occasioning actual bodily harm and was refused bail to appear in a children’s court on Thursday.

A crime scene has been established and will be examined by specialist officers.

Ashfield falls within the federal electorate of Grayndler, currently held by Prime Minister Anthony Albanese.

Voting is continuing as normal at the Ashfield pre-poll centre, said the Australian Electoral Commission.