A 33-year-old woman was sexually assaulted in Northall Street, Kettering.
The incident happened on Friday, July 11, when the woman was walking from Morrisons towards the Newlands Centre at about 2.30pm.
A man walked up behind her and grabbed hold of her bottom.
The man walked-off after being confronted by the woman.
He was black, 20 to 30 years, 5ft 7ins and of stocky build. He had short, black hair with a short beard and was wearing a long sleeved, tight, white top, purple and yellow basketball shorts and a diamond stud in one of his ears.
The incident took place near Farm Foods and police would like to speak to anyone who may have witnessed it, or who may have any information about it.
The information was released by police today (Monday, August 4).
Witnesses or anyone with information is asked to contact police on 101. Alternatively, phone Crimestoppers anonymously on 0800 555 111.