The home secretary has been urged to move the Yorkshire Ripper from Broadmoor high security hospital to serve the rest of his life sentence in prison.
Peter Sutcliffe said he heard voices
An MP says new evidence suggests Peter Sutcliffe - who murdered 13 women in the 1970s - had fooled psychiatrists.
Labour MP Fabian Hamilton, who represents the constituency in Leeds where the last victim, university student Jacqueline Hill was murdered, made his plea in a letter to David Blunkett.
Mr Hamilton said fresh evidence suggested Sutcliffe attacked and may have murdered a number of men in Yorkshire in the 1960s before he began what are now known as the Ripper killings.
He said this proved Sutcliffe's claim to have been directed by voices "to get rid of prostitutes" was false.
New revelations in a book about the police investigation meant that Sutcliffe hoodwinked psychiatrists before his trial, said Mr Hamilton.
The families of his victims and the Yorkshire public demand no less
The book, Wicked Beyond Belief, says Sutcliffe wore a specific piece of clothing for every murder, which "proves premeditation", according to the MP.
Mr Hamilton said he had known author Michael Bilton, who he described as a good researcher and journalist, for 25 years.
If Sutcliffe was "bad rather than mad", he must be treated like any other prisoner, he said.
"The families of his victims and the Yorkshire public would demand no less."
This would mean a transfer from the superior conditions at Broadmoor to a maximum security prison to serve the rest of his life sentence.
The hospital is "considerably more comfortable and less harsh than a
prison", according to Mr Hamilton.
Many police officers and psychiatrists working on the case were convinced at the time of his trial that Sutcliffe was mentally ill, and probably a paranoid schizophrenic.
Sutcliffe had said the motivation for his appalling string of crimes came from voices which first came to him in the cemetery where he was a grave digger.
But many others had doubts and suspected him of making a deliberate effort to feign insanity.
Sutcliffe is blind in one eye after being stabbed with a pen by a fellow inmate in 1997.