A Bradford psychologist today said the broadcasting of Ripper Peter Sutcliffe's voice on TV could spell extra trauma for relatives of his victims.

Tonight's BBC1 documentary will describe how dozens of women have become fascinated by the serial killer, and have written to him at his home at Broadmoor high security mental hospital.

The programme focuses on three of these women. One of them was sent a tape by the killer, on which he had recorded a message for her. When it is played during the documentary, it will be the first time the Ripper's voice will have been heard on television.

Today Dr John Cromby, pictured, a social psychologist at Bradford University, said he thought the broadcast may have the effect of 'humanising' the mass murderer.

"By letting Sutcliffe speak on this programme, it humanises him and makes him less of a demon," he said.

"The fact that he might be a real person, not a demon, is even more disturbing."

And the mother of one of the 13 women killed by Sutcliffe, Avril Hiley, denounced the show as "sensationalist" and the Ripper's women penpals as "sick".

Mrs Hiley's daughter Josephine Whitaker was just 19 when she became Sutcliffe's 11th victim.

The Halifax Building Society clerk was walking back to her parents' home from her grandparents' home late at night when she was beaten to death in April 1979.

Mrs Hiley said: "Fortunately we are flying out on holiday today.

"The whole thing is mindless titillation. These women are all sick, obviously.

"It's all so long ago now. I just think it should be left untrammelled.

"Every so often it rears its head in one way or another and they say they're looking at a new angle, but really they're trying to make the odd buck or two by being sensationalist."

Dr Cromby added: "If people haven't worked through their grief and are still raging and hurting, then no matter how sensitively a programme is handled, they won't like it, and will wish people had left it alone."

BBC spokesman Helen Martin said: "The programme is non-judgemental."

l Letters to the Yorkshire Ripper - Everyman, is on BBC1 tonight at 10.40pm.