Detective Chief Inspector Neil Jamieson, the officer in charge of the inquiry, said extensive work with CCTV footage together with information from house to house inquiries and calls from the public, had provided some important leads.

“We are determined to trace this young man and we are making steady progress. However, although we have had a number of callers in response to our appeals, I am sure there are other witnesses who have yet to come forward.

“We need people to contact us. Call 101 and ask for Shrewsbury CID if there is a possibility you saw the offender or his victim.

“And if you think you know his identity, then please tell us because we will be able to eliminate them from the inquiry if they were not involved.”

The assault took place at an isolated spot on disused land near the Arc car wash centre off St Michael’s Street, heading out of the town centre towards the fire station and Ditherington.

It happened between 3.30pm and 4.30pm on Friday (11th April) when scores of vehicles were passing in and out of town. There were also a number of pedestrians around at the time.

DCI Jamieson said today fresh information indicated the offender – a youth aged around 13 to his late teens – was in the area of New Park Road and St Michael’s Street several hours before the assault.

“We believe he was passing to and fro from New Park Road into St Michael’s Street from as early as 12.30pm on Friday, most of the time carrying a fishing rod and what appears to have been a fishing tackle box.

“The fishing rod should have made him stand out and I am appealing to anyone who might have spotted him, to contact Shrewsbury police station as a matter of urgency.”

The youth, who may be of secondary school age, is known to have followed the little girl along New Park Road into St Michael’s Street, turning right and soon after approaching her.

He persuaded her to help search for something he claimed to have lost and then lured her to an isolated location behind a container where the assault took place.

The suspect is described as white, about 5ft 7ins tall and likely to be in his teens. He has dark hair and was wearing a light and dark hooped pattern jumper or top, with light blue trousers or jeans and white shoes or trainers.

The little girl was also conspicuous carrying a large rucksack on her back.

DCI Jamieson said: “We know the offender was carrying a fishing rod for at least some of the time he was in the area, although at one stage, he may have been without it. He was also wearing quite a striking hoop patterned jumper or top.

“There is a strong possibility that he is local to the area where the offence took place. However, we are also extending our inquiry area to include the Greenfields locality which can be reached quite easily from where the offence took place”.

He added: “I cannot stress enough how important it is for people to speak to us if they have any information, or if they possibly saw the youth and young girl, either separately or together last Friday afternoon. Do call 101.”

Information can also be given to the anonymous Crimestoppers charity on 0800 555 111, or via its website, www.crimestoppers-uk.org.