World War Two resistance accounts say Mussolini was executed by a partisan fighter "in the name of the Italian people" after he was captured in April 1945 while fleeing Allied forces with his mistress.

"All lies," said Luciano Randazzo, Guido Mussolini's lawyer, in an interview with Reuters. "The real story is not what they told you ... Absolutely not."

The accounts name the executioner as the late Walter Audisio, also know by his war name "Colonel Valerio". They say the execution took place at the gates of a villa overlooking Lake Como in northern Italy.

Randazzo, who said he lodged the request with Como prosecutors on Aug 27, said that research showed Audisio was not even mentioned as the executioner until two years later.

The prospect of an exhumation threatens to provoke a family tug of war. Mussolini's better-known granddaughter, Alessandra, told Reuters she opposed an exhumation.

"Apart from the fact that we don't know about this request, it should come unanimously (from Mussolini's heirs)," the right-wing politician said. She suggested the truth about Mussolini's fate could come through more historic research.

"My grandfather ... should be left in peace."

Partisans found Mussolini and his mistress, Clara Petacci, and high officials of his rump fascist republic hidden in a retreating column of Nazi troops headed for Switzerland.

Their corpses were moved on April 29 to Milan and hanged upside down for public view at a petrol station in Piazzale Loreto, the square where fascists had executed 15 partisans in August 1944.

An exhumation would revive speculation about the dictator's final moments, long the stuff of legend and controversy.

The resistance fighter who captured Mussolini, Urbano Lazzaro, said in 1995 that Mussolini and Petacci had been dead for four hours when their partisan "execution" took place.

Citing a partisan he said had been present, Lazzaro said the couple died some way from the reputed site when Petacci tried to grab a gun from one of the guards who were escorting them to Milan for Mussolini's planned public execution.

"She was screaming 'They want to kill you'. Two or three shots went off in the struggle and hit Mussolini who dropped in agony. They finished him off on the spot and then shot Petacci for causing the accident," said Lazzaro, who died in January.

"The rest was all staged."