The detective leading the hunt for missing chef Claudia Lawrence today said the investigation had been classified as suspected murder.

Miss Lawrence, 35, was last seen five weeks ago near her home after she finished work at the University of York’s Goodricke College.

At a news conference in York, Detective Superintendent Ray Galloway said: "At the moment we have no proof of Claudia’s death. However, five weeks on from her disappearance we also have no proof of her life.

"The investigation is now being formally classified as one of suspected murder."

Mr Galloway said he had not given up hope but was ``looking at this investigation from a technical perspective''.

Miss Lawrence’s father, Peter Lawrence, who was at the news conference, said he understood why the police were now treating his daughter’s disappearance as murder but said he believed she was still alive.

He said: "It is necessary for their investigation but we believe that Claudia is still alive and that is what keeps us going and motivates us.

"I believe and the family believe very much that Claudia is still alive and we very much hope she is alive, that is what is keeping us going here.

"The sense of hope is clearly there."

Mr Galloway also disclosed new "significant" lines of inquiry after information from members of the public.

He said one person reported seeing a man and a woman walking near the University of York between 6am and 6.30am on March 17 and March 19.

Another witness also saw a man and a woman at 5.35am on March 19 as he travelled down Melrose Gate, towards Heworth, where Ms Lawrence lives.

Mr Galloway said there was no specific interaction between the couple but said the man was wearing a dark hooded top with the hood up and was smoking a cigarette with his left hand, which was "unusual".