The 20-year-old victim was assaulted in The Griffin public house, in Boar Lane, at about 7.45pm on Saturday, March 14.
Police have released a CCTV image of a man they want to speak to.
Det Constable Lee Thimm, of Leeds District CID, said: “The suspect was among a group of men socialising at the pub. It has been suggested they could have been from the Wakefield, Castleford or Pontefract area.
“I would like to hear from anyone who recognises the man or who has any information that could assist the investigation.”
The man was described as white, aged in his early forties, about 5ft 10ins tall and of average build. He was wearing jeans and blue jacket.
Anyone with any information is asked to contact Det Con Thimm at Elland Road police station via 101 or Crimestoppers, anonymously, on 0800 555111.