A man was attacked after challenging a group of youths who were urinating in the doorway of a bank in Cleckheaton.
The 30-year-old victim was assaulted by the group of five white men, aged between 18 and 22, in Northgate, at around 3.20am on Saturday.
Officers from the Spen Valley Neighbourhood Policing Team believe the five suspects may have been drinking in the George pub shortly before the incident and made their way to a taxi office in Northgate afterwards.
One of the suspects was slim, around 5ft 7ins tall and wearing a pink t-shirt. Another was similar height and stocky with close cropped brown hair and wearing a white t-shirt. A third man wore a red and white striped t-shirt.
The victim, who was with two friends, suffered facial injuries and needed hospital treatment.
Anyone who saw the incident or this group drinking beforehand and who can identify them is asked to contact PC Phil Miller at the Spen Valley Neighbourhood Policing Team on 101 or CrimeStoppers in confidence on 0800 555 111.