Michael Stone has been challenged by serial killer Levi Bellfield to take a lie detector test over the murders of a mother and her daughter, it has been revealed.

Stone, 56, from Gillingham, is serving three life sentences for the killings of Lin and Megan Russell, who were found bludgeoned to death 20 years ago on a country lane at Chillenden, near Canterbury.

He has always maintained his innocence.

It was suggested last year that Bellfield - who was convicted in 2011 for the murder of 13-year-old Millie Dowler - was the killer. He resembled an original photofit issued following the killings.

But the Met Police ruled out any possible links following an inquiry across 10 forces, which began in January 2015.

In a six-page statement obtained by the Sun on Sunday, Bellfield denies the murders and revealed he has asked Stone to take a polygraph test with him, over the Russell murders.

Bellfield claims that Stone has refused to take the test. The statement is signed in his new Islamic identity, Yusef Rahim, and refers to himself in the third person as LB.

According to the Sun report, he said: “LB even invited Mr Stone to choose an expert and also the questions that should be asked.

“Given that Mr Stone and LB are both located at HMP Frankland, it was a relatively easy task to undertake.

“He keeps saying, ‘It was not me, it was LB’. While Mr Stone seeks to hide behind this mask, unfortunately for him it will not overturn his convictions.”

Bellfield said his family would pay for an expert to conduct the tests and, although they will not be legally admissible, he said: “it would be a public platform for him to back up his innocence campaign.”

Bellfield added: “The results could also be used to stop blaming LB should he also pass the polygraph test. LB thus invited Mr Stone’s legal team on several occasions to participate in the polygraph test, but to no avail.

“Various excuses were put forward such as a lack of financial resources amongst other things. Indeed, there were other times when the requests for the test were simply ignored by Mr Stone.

“If, as Mr Stone says, he is innocent, then then why refuse to take the polygraph test?”