Fresh doubt could be cast over Michael Stone's conviction for the notorious murders of mum Lin Russell and her daughter Megan, aged six following the confessions of a brutal killer.

Stone, 56, from Gillingham, has served 19 years of a life sentence for the savage hammer attack of the mother of daughter in Chillenden, near Canterbury in July 1996 - but he has consistently protested his innocence.

Now, Levi Bellfield - who is serving a full life term for the murder of Milly Dowler - has finally admitted that he did kill the schoolgirl after abducting and raping her.

Bellfield has this week revealed that he was also behind a string of other brutal attacks.

Although there has been no official confirmation, there has been speculation that these could include the case of the Russells, who died in a frenzied hammer attack in a country lane with their dog Lucy.

Mrs Russell's other daughter Josie, nine, was seriously injured, but has made a full recovery.

Former heroin addict Stone who used to live in Skinner Street, has always insisted that he did not carry out the murders and has said that detectives should question Bellfield about it.

Stone was convicted at two trials and also lost an appeal.

But no forensic evidence linked him to the scene of the crime and his conviction relied largely on the so-called cell confession evidence of a fellow prisoner, Damien Daley.

Daley, also a former drug addict who admitted in court to be an accomplished liar, has himself since been jailed for murder.

Because Stone is still proclaiming he did not do it, he will have to serve the full 25 years of his sentence unless new evidence comes to light.

If it emerges that Bellfield has confessed to the Russell case, Stone's conviction would have to reviewed.

In addition to the murder of Milly Dowler in 2002, Bellfield is also serving life terms for killing Marsha McDonnell and Amelie Delagrange.

Bellfield's dramatic revelations have sparked new investigations which could involve police forces across the country.

A spokesman for Kent Police would not confirm if they had been contacted by the Metropolitan Police, which is leading and coordinating the liaison between forces.