A new book alleges Lindsay Rimer was killed by the same man who murdered schoolgirl Caroline Dickinson at a hostel in France.
But the claim that Francisco Montes is responsible for her death has never been passed on to West Yorkshire Police or Lindsay's mother Geri, who still lives on Fountain Street, Hebden Bridge.
The information is believed to have come from a retired policeman but author Wensley Kingsley would not confirm which force the officer had worked with. He was also unable to confirm whether he had concrete evidence that Montes was in Hebden Bridge on the day Lindsay disappeared. But he said the convicted killer had visited York while working as a waiter at a London hotel.
Despite this, The Predator: Portrait of a Serial Killer alleges Montes travelled from London to Hebden Bridge on November 7, 1994, and spotted Lindsay. Mr Kingsley claims she got into Montes's car after he offered her a lift.
But Lindsay's mother feels the claims could be distracting attention from finding the person responsible for her daughter's death. She has been told about the book by West Yorkshire police officers working on the case.
"I am highly sceptical about these claims. All I want to do is find Lindsay's real killer," she said.
Senior investigating officer in the Rimer case, Det Supt John Parkinson, said the information had not been passed on to him.
"This is the first I have heard of it but we will look into any new claims."
Lindsay's murder has remained unsolved for 12 years but officers from West Yorkshire's homicide and major inquiry team are still working on the case and are in constant contact with her family.
The 13-year-old's body was found in the Rochdale Canal five months after she vanished.
A spokeswoman for West Yorkshire Police said officers would seek to establish the factual base of the claims made in the book.