The incident happened between 1.40pm and 1.50pm on Monday, June 6, when a 17-year-old girl was approached by a man in a ginnel off Woodnook Drive, Tinshill, and sexually assaulted.
The man was described as white, aged in his early fifties, skinny, about 6ft tall, with short dark brown hair and bald in the middle.
He was clean shaven and was wearing a dusty, brown suit, white shirt and green tie. He was carrying three carrier bags, which appeared to contain clothing.
Anyone who recognises the man or who has any information that could assist the investigation is asked to contact Detective Constable Karen Glover at Weetwood police station via 0845 6060606 or contact Crimestoppers, anonymously and in confidence, on 0800 555 111.