The father of a 22-year-old man accused of having a relationship with a girl of 12 says the two are just "close friends".

Liberal Democrat Norman Baker, MP for Lewes, made the case public in a bid to change the law after police said they could do nothing.

The girl's distraught parents contacted Mr Baker after they feared their daughter was having sex with Luke Salmon, of Mill Lane, South Chailey, near Lewes.

Mr Baker said he would be writing to Prime Minister Tony Blair about the claims, which Sussex Police say they are powerless to act upon.

Despite her parents offering evidence, including a pregnancy test found in the girl's bag, items of clothing and her mobile phone, the police say they cannot act unless the girl makes a complaint.

They could not force her to be examined, test her clothes or look at messages on her mobile phone as it went against human rights laws.

However, Mr Baker, who is on the Human Rights Committee in Parliament, said it was ridiculous laws brought in to shield people prevented the girl from getting the protection she needed.

He said: "I will be writing to the Prime Minister again and talking to the police again to see whether they will review the situation.

"Here is someone who is young and vulnerable in what looks to me to be a wholly unsuitable relationship with a 22-year-old. She could come out of this emotionally scarred. That is my concern and that of her parents as well."

He said his aim was to find out if the Government believed the law could do more and if not said there was a clear case for the law to be amended.

He said: "It's difficult for the Government because it cannot be seen to be interfering in an individual case.

"The Prime Minister is going on about making parents responsible for the actions of their children but when you have responsible parents who want to give love and care the legislation, or the attitude of the authorities, stops them.

"I'm not convinced that the police can't do more. This has been going on for three months now."

The girl's mother said she and her husband were crying out for somebody to help them and their daughter, who was being "destroyed".

She said: "We are living a nightmare. It feels like she has died but she hasn't.

"We saw her this afternoon but it wasn't our daughter. She has been destroyed, I hope not forever. We still love her so much and respect her for all her good qualities."

She added that she has cried every day for the past few months after contacting numerous solicitors, social workers and police officers with nobody being able to help.

The mother said: "Tony Blair has a young daughter. How would he feel if he was in our position? We are so frustrated that nobody can help us.

"A change in the law might be too late for our daughter but it could save other parents."

Luke's father told The Argus his son was innocent of all the accusations, adding: "Luke has been plastered all over the papers and his name blackened but there are two or three sides to every story.

"The fact is they are close friends. That is all there is.

"The situation has been pushed a certain way by her parents' actions and they have become good friends but the police and social services were aware the whole time.

"Nothing has been done behind anyone's back. Luke has done nothing wrong. It will all come out in the next few months. Luke has no choice but to cope and for the moment he is just keeping his head down."

The girl's parents told a Sunday newspaper they were in a state of shock.

The girl's father said: "We believed the social services and the police could stop it but we discovered there is nothing illegal about a grown man having a relationship with a child unless you can prove it's sexual."

The mother said: "The system is barmy. I took away her clothes when she came home after spending the night at his and got in the shower.

"I hid them for the police because I felt there could be evidence of a sexual relationship but they said they couldn't do anything until she made a formal complaint.

"It was the same when we gave them our daughter's phone. The police said they could not unlock it without our daughter's permission.

"It seems ludicrous that when something like this happens, the only person who can make a complaint is the brainwashed victim."

A spokesman for Sussex Police said: "In this particular case we fully investigated but in the absence of first-hand evidence from the child it is difficult to progress further."