The former husband of Ashtead murder victim Sharon Birchwood is formally being treated as a suspect in her murder investigation, his father has claimed.

A car belonging to Graham Birchwood's father is also being held by detectives who want to conduct a thorough forensic investigation on it. The vehicle was taken after it emerged Graham had been using it when he found her body in Harriotts Lane on Friday, December 7.

His father, Colin Birchwood, from Epsom, said that after the police had confiscated his car, they had offered to pay the bill if he hired a car or used mini cabs.

"I don't need it though," he said. "I live so close to town and I wouldn't want to use the system like that, I just want Graham to get off the hook."

Mrs Birchwood's body was found bound and gagged at her home. She had died from asphyxia about 24 hours before her body was discovered by her ex-husband.

Speaking of the circumstances surrounding her death, Colin Birchwood described it all as "a bit kinky".

He said his son was a disc jockey and stored many of his records in the loft space at Mrs Birchwood's house, often letting himself in to retrieve them if she was not at home. He said his son had been a suspect in the case from the very beginning.

He added: "He's been interviewed by the police quite a few times. He said the officers were all very friendly and all on first name terms with each other. Graham's no murderer, but there's a couple of people that would spring to mind. But the police haven't contacted me so I haven't mentioned it."

Graham Birchwood remarried after his divorce with Sharon and had two teenage sons, with one starting university in September, studying for a business studies degree. Colin Birchwood said that it was a relief for him to move away to university and escape from what was going on.

He said: "It's so sad to see what it's doing to the family. Graham has very bad diabetes, he's lost a few toes from it and all of this is just making it worse."

But he said that reports that his former daughter in law was in denial about her divorce with his son and told friends that he was simply away travelling had confused him.

"He does travel, but he's not really a traveller of sorts. He has interests in the far east but I'd rather not know what it is," he said.

A Surrey Police spokesman said: "We will never comment on the details of an investigation while the investigation is in progress. "Until there is sufficient evidence to charge an individual with an offence, investigating officers will keep an open mind. "Many items have been removed for forensic examination in addition to the forensic work at the scene. This detailed work forms part of the investigation on which we are not prepared to comment."