The sister of the man convicted of the brutal murders of Lin and Megan Russell says she believes Levi Bellfield's "astonishing" confession is "absolutely true".

Barbara Stone is convinced the serial killer's admission he attacked the mother and her six-year-old daughter in Chillenden in 1996 will finally prove her brother Michael did not do it.

The 61-year-old Gillingham resident, who is serving life for the savage murders which rocked the nation, and has always professed his innocence.

Ms Stone, who has campaigned tirelessly for his freedom, said: "This is not just Bellfield chin-wagging.

"Nobody is going to come out with a statement like that over such a terrible crime.

"I have believed Bellfield for a long time but never thought he would have the guts to formalise a statement that can be used as evidence.

"It was a difficult decision on his part I'm sure as he may experience a lot of consequences particularly among his fellow prisoners.

"He has described his movements that day in great detail how he committed the murder and even what he did with implements used.

"My heart goes out to the Russell family who have endured endless pain as we seek to prove Mick is innocent.

"I think it is in all our interests to have this matter investigated when there is a realistic possibility it could bring closure.

"Bellfield has done this the right way and voluntarily.

"I don't believe he would have made this confession if his mother was still alive."

Ms Stone is now demanding an independent police force takes over any future investigation.

She said: "I believe there is a conflict of interest with Kent Police.

"It has to be done the correct way through the correct legal process."

She said her brother shares her request to have another force handle the case.

She said: "Bellfield has come out with a lot of facts that can be checked including information about the murder weapons."

Killer Bellfield has passed a four-page statement of admission to Stone's lawyers.

It is a development which will fuel claims of a miscarriage of justice

In it he confesses to being responsible for killing Lin, 45, and Megan, six, with a hammer, and leaving her sister Josie, nine, for dead.

His solicitor says it means Stone will "finally" get his freedom.

Paul Bacon told MailOnline: "I can say I have received a four-page statement from Bellfield, which is a genuine confession, it's an absolutely astonishing breakthrough.

"I will now meet with colleagues following this remarkable development to finally, after many years, get freedom for Michael Stone.

"This is the evidence that will prove he is innocent."

It has been reported by The Sun that Bellfield made the confession last month.

It reads: “I was wearing bright yellow marigold washing-up gloves and holding a hammer in my right hand.

“In my car I had a screwdriver, a lock knife, a hammer, yellow marigold gloves and a very long black bootlace.

“My first intention was to just attack Lin, but I quickly changed my mind due to the screams and was worried she would fight back given the children were with her.

“I approached Lin and held her right arm tight. She asked me not to harm her children. She was calm.

“Had she screamed I would have attacked her and left not harming the children.

“The situation just got out of control and the more she complied it just gave me more confidence.

“I walked all three of them off the track. I forced Lin to sit down.”

The statement goes on to detail how Bellfield killed Lin and Megan, and left Josie for dead with appalling injuries.

He also says he killed the family dog after it bit his wrist.

Bellfield, 53, is already serving life for the murders of Millie Dowler, 13, Amelie Delagrange, 22, and 19-year-old Marsha McDonnell.

He was also convicted of the attempted murder of Kate Sheedy, 18.

As well as admitting to murdering and Lin and Megan in the 14-paragraph statement, Bellfield, also reportedly admits to the murder of a woman called Judith Gold in North London in 1990.

He has previously admitted being in the Chillenden area at the time of the killings.

But his new statement provides new details, and reveals how after the murders he stopped at services on the M25 in Surrey to wash off blood.

He said: “On my return I stopped at Clacket Lane Services and cleaned up.

"I used my t-shirt to clean myself and wipe my shorts. I used bottled water. It was warm and I drove the rest of the journey with no top on. I didn’t look out of place.”

Bellfield then tells how he went home to Twickenham got changed and went to work as a nightclub bouncer.

He says the following day he threw the hammer into the Thames near Walton, Surrey.

He then went on holiday to ­Turkey, but claims he returned to have the beige Ford Sierra he was driving on the day of the murders cleaned, fearing it was full of DNA.

The confession document will now be sent to the Criminal Cases Review Commission, which has the power to order re-trials and is considering an appeal by Stone.

The former drug addict has always denied responsibility for the killings.

He was convicted in 1998 and then again in 2001 after the original convictions quashed.

An appeal against the convictions in 2005 was unsuccessful.

Bellfield ends his statement, saying: “Something like this has never happened to me, in the sense I’ve committed a crime and another person has been arrested for it.

“I apologise to Stone and the Russell family for my heinous acts.”

Reacting to Bellfield's confession, Detective Chief Superintendent Paul Fotheringham said: "Following two trials at which Stone was found guilty by a jury on both occasions, and an appeal to the High Court, he remains convicted of the murders and attempted murder.

"Michael Stone made an application to apply for a Judicial Review in respect of his conviction in September 2012. The Honourable Mr Justice Blake ordered that permission for the application should be refused.

"The Criminal Case Review Commission (CCRC) commenced an extensive re-examination of the murder investigation in 2017 and has had access to all forensic evidence, documentation and exhibits from the original investigation, the review by Hampshire Police, details of the two crown court trials and appeals to the High Court.

"The shoelace which was seized as part of the original investigation was made available to the CCRC.

"All evidence from the examinations on the shoelace were recorded and disclosed to the CCRC."