MILAN (Reuters) -Ferrari and Stellantis chair John Elkann faces a new legal battle with his mother after her lawyers on Monday presented what they said was a previously undisclosed handwritten amendment to the will of her father, the late Gianni Agnelli.

The note, produced during a court hearing in Turin, could raise questions over the ownership of the holding company at the top of Exor, the Agnelli family investment firm led by Elkann that controls sports car maker Ferrari and is the top investor in Fiat-to-Jeep maker Stellantis.

The holding company, called Dicembre, is owned by Margherita Agnelli's three children from her first marriage: Elkann and his siblings Lapo and Ginevra.

ELKANN'S LAWYERS SAY DOCUMENT IS NOT RELEVANT

Margherita Agnelli is locked in an inheritance dispute with the three of them over Gianni's estate after his death in 2003.

The handwritten note, dated January 20, 1998, was filed at a hearing on Monday, according to her lawyers, as part of the civil case which she has brought in proceedings that are dividing one of Italy's best-known families. Reuters has also seen a copy of the note.

In the signed note, Gianni Agnelli stated that his roughly 25% stake in Dicembre should be assigned to his son Edoardo, who subsequently died in 2000. A separate document from 1996 had indicated that the shareholding should go to John Elkann, his grandson - which is what happened.

John Elkann's legal team said the alleged new document had no bearing on agreements reached in 2004 about Gianni Agnelli's estate.

The note was found during a separate criminal investigation by the Turin prosecutor's office into alleged tax evasion that ended this month with Elkann agreeing to a year of community service.

When Gianni Agnelli's will was opened in February 2003, the heirs had information only relating to the 1996 document, Margherita Agnelli's lawyers argued.

As a result, Gianni's widow, Marella Caracciolo donated a 25.37% stake in Dicembre to Elkann, enabling him to gain a majority.

Margherita Agnelli's lawyers say that their client and Marella Caracciolo should have kept the portion of Dicembre intended for Edoardo.

She inherited 1.2 billion euros ($1.4 billion) after her father died but wants a greater share of the estate for her five children from her second marriage.

"The management of the Agnelli estate was established with the settlement agreement of February 2004, following which Margherita definitively withdrew from Dicembre's capital," Elkann's lawyers said.

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