Two schoolgirls yesterday described their "shame and disgust" after agreeing to kick a married driving instructor in the groin.

They told a jury at Oxford Crown Court that David Aston, 32, drove them to secluded woodland near Bicester and performed a sex act with their friend in the front seats of his Honda car.

They said Aston, who denies sexual activity with a child, causing or enticing a child to engage in sexual activity and making indecent photographs of children, got out of the car, bent down on his hands and knees and asked them to kick him in the groin.

One girl, 14 at the time of the alleged incident, said she felt sick when her friend explained what Aston, of Bell Close, Cassington, wanted them to do. During a taped interview played to the court, she said: "I could tell by my friend's face if I did not do it then there would be some arguments because she did not want to be the only one there doing it.

"As I did it I just closed my eyes because I did not want to be there.

"After that had happened I just felt so sick and nasty."

When asked how she felt about the incident, she said: "Stupid. Because I met a complete stranger, it could have been about ten-times worse. He might not have taken me home.

"I was disgusted with myself I actually went through with the whole kicking thing."

She added she kept quiet when her friend lied and told Aston she was actually 15.

Another girl, 13 at the time but who told Aston she was 14, said: "I felt ashamed, stupid. My mum has told me never to get in a car with strangers and I did. I should not have gone."

A third girl, also 14 at the time, said another friend told Aston they were all 16.

She explained they were introduced to him after another girl met him in an Internet chatroom. Aston was logged on with the name: "I will show you mine if you show me yours".

The teenager said he promised to give them alcohol or cash if they agreed to his requests and said all three girls had shared two bottles of cider. She also admitted engaging in consensual sex acts with Aston.

Claire Fraser, defending, suggested the girls had told Aston they were 16 and that the first two girls had been drinking, which they denied.

She emphasised they had not been forced to do anything by Aston.

Miss Fraser also suggested that when the girls said their friend performed a sex act on Aston, what they had seen was actually a hug.

The trial continues.