A 57-year-old social worker has been acquitted by a court of behaving in a sexual way with a young girl under his supervision.

Keith Butler was alleged to have commented on how nice the teenager’s breasts looked and on one occasion patted or smacked her bottom.

But the former probation officer denied that he had behaved inappropriately with the girl and was unanimously cleared by a jury at Maidstone Crown Court.

Oliver Saxby, prosecuting, had told the court: "In short, the Crown say he abused his position of trust and became over-familiar in an overtly sexual sense."

Mr Butler, of New House Lane, Canterbury, was supervising the girl who had been placed with foster parents in St Mary’s Bay in July last year. He was based at the Brockman Family Centre in Folkestone and was the girl’s first social worker.

Mr Saxby said one of the foster parents formed the view very early on that Mr Butler’s relationship with the girl was over-familiar.

A few days later, Mr Butler went to the house to see how things were going and there were discussions in the kitchen.

The wife bent down to pick something up and saw that the girl had her legs resting on Butler’s lap, said the prosecutor.

"Neither, though, seemed the least bit uncomfortable about this," he said. "In fact, far from it. According to (the foster parents), they seemed to be acting like best of friends."

After the girl got off her stool, the mother saw that her knickers were showing above her waistline and made a comment about it. Butler commented: "It would be better if you didn’t have any."

Mr Saxby told jurors: "If it had been a joke, it wouldn’t have been a very good one. After all, she was just 13 and Mr Butler was the social worker assigned to look after her."

About a week later, Butler went with the girl to a beach and then took her home. They discussed what they had been doing and it was a standing joke that he had been looking at girls in bikinis.

The girl went to the toilet and when she returned had paper stuffed in her bra and said her boobs were now bigger than her foster mother’s.

"Mr Butler joined in with some remark of his own," said Mr Saxby. "As she took the lavatory paper out, once more Mr Butler passed comment on her knickers."

The girl told police that Butler had become over-familiar with her. He had paid her compliments "that should not be coming from him", she said, and on her 13th birthday he patted or smacked her bottom.

Mr Butler, who denied sexual activity with a child, said the girl was "mixed-up" and he disputed all of the allegations.

The prosecutor said girls in the teenager’s position needed a strong, reliable and straightforward relationship, where the boundaries were not blurred. "What she got was far more than that," he added.

The jury returned the not guilty verdict on Monday after deliberating for less than one-and-a-half hours.

Judge Warwick McKinnon told the jurors: "Thank you for the obvious care and attention you gave to what I thought was a difficult case." Mr Butler was granted £237 costs.