It happened at around 8am when a 14-year-old girl on her way to school was followed by a man along a shortcut path from Heron Way in Oswaldtwistle.
When she reached Town Bent Lane, he has run up to her, grabbed her buttock and then ran off.
The September 27 incident followed a similar incident that happened in March where a man ran up to another 14 year old girl, also on Town Bent Lane and touched her before running off.
The man pictured is described as white, aged between 20 and 30, short and was wearing a black hat and black clothing.
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DC Kirsty Stephenson from East CID said: “The release of this image follows our previous appeal we asked for the public’s help on earlier this month. Our search is very much on-going and we are determined to find the man responsible.
“Do you know someone who looks like the man in this image? If yes, we need to speak to you as soon as possible. If you’re unsure or you think it could slightly resemble someone you know, please still make contact with us.”
You can email DC Kirsty Stephenson on [email protected] or can call 01254 353628. If you fail to get an answer, please dial 101 and quote incident reference 279 of September 27th.