Man critical after assault in Sydney

A 55-year-old man is in a critical condition in hospital with head injuries after being assaulted in Sydney's inner west at a university function hall.

Emergency services were called to the hall at Camperdown at about 7pm on Saturday to find the man unconscious on the ground.

Ambulance paramedics treated him for head and facial injuries before taking him to Royal Prince Alfred Hospital.

Police were told the man was approached by another man who punched him, causing him to fall to the roadway.

A 40-year-old man was arrested nearby and has been charged with recklessly inflicting grievous bodily harm to appear at Newtown Local Court on June 15.