A Victorian policeman retained his job and rank despite being caught on CCTV repeatedly slapping a drunk disability pensioner before hurling him to the ground and knocking him out, leaving the man with ongoing injuries.

CCTV footage shows Sergeant Michael Cooke repeatedly slap 62-year-old Phil Dickson in the back of the head and then throw him to the ground at Geelong police station in January 2013.

Images from CCTV footage showing the assault on 62-year-old Phil Dickson.

Mr Dickson, who was hospitalised after the attack, does nothing to justify the use of force.

Revelations about the handling by police of the assault on Mr Dickson come amid growing pressure on the state government to back reforms of the police complaints system.