Detectives are appealing for information following a report of a sexual assault outside The Lounge bar in Lancaster.
Around 5.30am on Sunday, December 16, a woman was sat on the floor at the side of the pub when a man sat beside her and attempted to touch her inappropriately.
The woman told the man to stop and alerted door staff and police were called.
Officers arrived and whilst they were in the process of speaking with witnesses the woman left the scene.
Detective Constable Ian Wright said: “Officers were able to speak to the woman briefly at the scene, however she left before they could get any further details from her.
“We would urge her to come forward, as well as anyone who may have any information which could help with this inquiry.”
Contact police on 101 or Crimestoppers anonymously on 0800 555 111.