Court papers reportedly claim French fashion boss Gerald Marie hired the killer to “deal with” Lisa Brinkworth after she went undercover to expose his agency Elite Model Management.
They suggest Ms Dando may have been gunned down on her doorstep in a case of mistaken identity because of similarities in the appearance, occupation and addresses of the two women.
Lawyers also said Ms Dando’s fiancé Alan Farthing was Ms Brinkworth’s doctor, according to the Daily Mail.
Mr Marie, 72, is being investigated in France over multiple accusations of alleged sexual assaults – which he strenuously denies.
Ms Brinkworth alleges she was assaulted by Mr Marie in 1998 while working undercover on a BBC exposé about sex crimes in the fashion industry.
Lawyers in the documents submitted to a court in Paris refer to a conversation witnessed by former Elite executive Omar Harfouch in which Mr Marie allegedly ordered a member of the Russian mafia to “deal with a problem”, the Daily Mail reports.
The papers from French law firm Bourdon Associes reportedly state: “Shortly thereafter… a BBC journalist, Jill Dando, was shot dead in April 1999.
“Indeed, these two journalists were in their thirties, were blonde with the same facial features, of the same height and of similar stature.
“They lived close to each other and had people in common, including the husband of Jill Dando.”
Ms Dando, 37, was shot dead outside her home in Fulham, west London, on 26 April 1999.
The hunt for her killer went on to become the biggest murder inquiry conducted by the Metropolitan Police and the largest criminal investigation since the hunt for the Yorkshire Ripper.
Barry George spent eight years in prison after being wrongfully convicted of killing the Crimewatch presenter. In August 2008, Mr George was acquitted of the crime at retrial.
He was the only person ever to be put on trial for Ms Dando’s murder.
A spokesperson for the Metropolitan Police said: “The investigation into the murder of Ms Dando remains open, as with all murder investigations.
“We will always explore any new information which may become available.”