* CEO Marchionne gets more labour flexibility at car plant
* Deal will unlock $1.3 billion of investments
* Agreement is part of "Fabbrica Italia" investment project
* Fiat will not apply national contract at plant -unions
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By Gianni Montani
TURIN, Italy, Dec 23 (Reuters) - Fiat's boss Sergio Marchionne scored another victory in his struggle to boost productivity at loss-making Italian car plants by clinching a labour deal with unions for the group's key Mirafiori plant.
The deal, signed by all trade unions with the exception of left-leaning FIOM, will unlock $1.3 billion investments at its Mirafiori plant to build top-range SUVs, granting a future for the historic Turin plant.
"A deal on the Mirafiori plant has been reached," read a statement from Italian trade union Fismic, which signed the agreement.
The deal, which comes on the back of a similar, landmark accord at Fiat's Pomigliano plant in southern Italy, is another step in Chief Executive Marchionne's "Fabbrica Italiana" project foreseeing 20 billion euros of investment in Italy in exchange for less labour rigidity.
Under the agreement Fiat will not apply Italy's rigid national contract law to the Mirafiori plant and will ban all union activity for those that did not sign the deal, union sources have told Reuters.
A workers' referendum on the deal is likely to take place in January.
Fiat, which is struggling with dwindling car sales in Europe, boosted its 2010 targets in October after third-quarter results raced past forecasts with strong truck and construction equipment sales. ($1=.7613 Euro) (Reporting by Gianni Montani, Writing by Lisa Jucca and Danilo Masoni; Editing by Jon Loades-Carter)