The incident happened at midnight on Friday 29 April into Saturday 30 April inside Normans Bar on Call Lane. A 28 year old man from the Manchester area was left with a broken jaw.
The suspect is described as white, in his mid 20s, 5’11” tall, of slim build and with short blonde hair at the side and longer on top.
He was wearing a long sleeved white shirt and blue jeans.
He was removed from the premises by door staff.
Any witnesses are asked to contact DC Damian Hunt on 0845 6060606 or the independent crime fighting charity Crimestoppers on 0800 555111.