Lawyers for Michael Stone, twice convicted of the hammer murders of Lin Russell and her daughter Megan, say they have obtained evidence of a prison confession from Levi Bellfield that he carried out the murder.

Paul Bacon, solicitor for Mr Stone, told a press conference that Bellfield's alleged confession contains factors that are not in the public domain.

"We have now received evidence of a full confession by Levi Bellfield," Mr Bacon said. "He has admitted the Russell murders."

"In the confession, Bellfield describes how he came across Lin Russell and her two children, how he attacked them with a hammer and he explains his motivation for the killing. The confession is detailed and has a number of facts which are not in the public domain."

The confession was made "not just once" to a fellow prisoner by Bellfield, the legal team claim and is "detailed and includes diagrams".

It came about following a two-part BBC documentary aired in May which saw a panel of independent experts re-examine the evidence and suggest another suspect, the lawyers said.

The legal team have also discovered new forensic evidence backing their case, Mr Bacon said.

After a review of the case papers, they have also found an independent witness "who saw Levi Bellfield close to the scene of the murders about the time they were committed."

The legal team have now sent the new material to the Criminal Cases Review Commission (CCRC).

The legal team are requesting that it is referred to the Court of Appeal quickly and that a new investigation is carried out by an independent police force from Kent Police who investigated the case previously.

Mr Bacon added: "The Russell murders by Levi Bellfield fits perfectly with his modus operandi. He is a man known to attack and murder women, his weapon of choice is a hammer."

Michael Stone is serving three life sentences for bludgeoning Lin Russell and her daughter Megan, six, to death in an attack near Chillenden in Kent in 1996 in which her other daughter, Josie, nine, suffered severe head injuries and the family's dog, Lucy, was killed.

Mr Stone, who has fought a protracted legal battle to clear his name, was also convicted via prison confessional evidence.

Damian Daley, who helped convict Stone, has since been jailed for murder.

He said Stone confessed to the hammer murders through a heating pipe into the next cell at Canterbury Prison.

It is not the first time Stone's legal representatives have pointed the finger at Bellfield - in 2011, his solicitor, Paul Bacon, claimed Milly's killer was a better match for the e-fit of the suspect issued during the police manhunt.

Mr Stone's sister Barbara, who attended the press conference, said that she and her brother "hopeful".

"It is the biggest hope that my brother's had for a long time," Ms Stone said.

"He has been in prison for 20 years and that's 20 years too long for someone who hasn't committed a crime."

Stone was told in 2006 that he must spend a minimum of 25 years behind bars over the attack on Dr Russell, 45, and her daughters as they walked home from a swimming gala along a country lane in July 1996.

Josie survived her injuries and went on to carve out a new life as an artist, growing up with her father, Dr Shaun Russell, in Wales.

13-year-old Milly Dowler was murdered in 2002 Credit: PA

Bellfield, who now calls himself Yusuf Rahim, is serving a whole-life tariff after being found guilty of abducting and killing Milly Dowler following a trial at the Old Bailey. He was jailed in 2011.

The 13-year-old was snatched from the street while on her way home from school in Walton-on-Thames, Surrey, in March 2002.

Josie Russell and the family of Milly Dowler have been informed about the new accusations, Mr Stone's barrister Michael McDonald said.

He was already in jail for the murders of Amelie Delagrange and Marsha McDonnell, and the attempted murder of Kate Sheedy, when he went on trial accused of killing Milly.

In 2008 he had been given a whole-life term for murdering Ms McDonnell, 19, in 2003, and murdering Ms Delagrange, 22, and attempting to murder Ms Sheedy, 18, in 2004.

Michael Stone, pictured here in 2001, has always maintained his innocence. Credit: PA

In November last year, the Metropolitan Police closed a probe into serious crimes allegedly involving Bellfield, saying all lines of inquiry had been "exhausted" and officers had found no evidence linking him to cases for which he had not already been convicted.

In October 1998, a jury at Maidstone Crown Court found heroin addict Stone guilty of counts of murder and attempted murder.

An appeal over doubts about a key witness saw the convictions quashed by Court of Appeal judges in 2001, before Stone was convicted again at a second trial at Nottingham Crown Court and, in October 2001, was given three life sentences.