MILANO (Reuters) -The holding company of late Italian billionaire Leonardo Del Vecchio has raised its stake in bailed-out lender Monte dei Paschi, a filing showed, strengthening its hand in expected further consolidation among the country's banks.

The move by Delfin, the holding company of the late eyewear magnate and Ray-Ban owner Del Vecchio, is the latest twist in a banking saga ignited by the Italian Treasury's placement of a 15% Monte dei Paschi (MPS) stake in November.

That sale handed Delfin a 3.5% stake. Francesco Gaetano Caltagirone, another Italian billionaire, also took 3.5%, while Banco BPM bought 5%.

The regulatory filing showed Delfin on Dec. 27, the day that MPS named five new directors, increased its holding to 9.78%.

The investment makes Delfin the biggest private investor in MPS after the Treasury, which holds 11.7% of the bank it rescued in 2017 - down from the initial 68%.

Italy's government had said the re-privatisation of MPS, which restructured under CEO Luigi Lovaglio in recent years, should contribute to building a third large bank next to heavyweights Intesa Sanpaolo and UniCredit.

The 15% placement raised the prospect of an eventual tie-up between MPS and Banco BPM and prompted UniCredit to launch a takeover bid for BPM, with CEO Andrea Orcel saying his bank could not afford to be sidelined as consolidation sped up.

UniCredit's bid for BPM threw a spanner in the works of BPM's own bid for fund manager Anima Holding.

Like Delfin, Caltagirone is positioned to play a role in any future bank M&A. The construction tycoon has raised his initial MPS stake to 4.97% and bought 5% of Anima. He has now two representatives on the MPS board, including son Alessandro Caltagirone.

Delfin and Caltagirone are also the leading investors in Milanese bank Mediobanca with stakes of 19.8% and 7.8%, respectively. They are also major investors in insurer Generali with 9.9% and 6.9%.

(Reporting by Elisa Anzolin and Alessia Pé; Writing by Valentina Za; Editing by Elaine Hardcastle and Deepa Babington)