Fiat is ratcheting up the pressure on its recalcitrant unions - and it would appear one in particular - as it looks to secure a productivity deal at its Italian Mirafiori plant.

Addressing a group of Fiat senior management in Turin this week, CEO Sergio Marchionne - not a retiring violet it would seem - had some tough words for his unionised workforce.

And they appear to echo what his spokesman also told just-auto, that one union in particular, namely Fiom, was behaving "more like a political party."

Of all Fiat's multi-lettered unions, Fil and Uilm among them, Fiom has opposed just about every twist and turn as the manufacturer attempts to impose its will, plant by plant across the country.

But Marchionne is determined to win this battle, even widening the debate to say Fiat must take note of what is happening in the rest of the world as it emerges from a post-crisis environment.

A copy of Marchionne's comments in Turin as he outlined the Fabbrica Italia project have been sent to just-auto and although he doesn't mention Fiom by name, he certainly appears to aim both barrels at hard-nosed unions.

"I have heard demands and threats." he said. "I have heard people demanding conditions in a way that seems more like a skirmish between warring factions than a dialogue between socially-responsible parties working toward a common objective.

"What they fail to realise is that the challenge before us requires everyone working together. They fail to realise they are playing with the future of our employees."

The Fiat boss adds one of his most difficult jobs was to explain "the complexity of industrial relations in Italy and the obstructive stance of unions, albeit a minority, toward the creation of conditions that would enable the country to develop. Because it is something absolutely absurd, beyond comprehension."

Not once does Marchionne mention a union by name, but he certainly refers to unions in general and Mirafiori in particular, heralding improved productivity as benefiting employees as well as Fiat.

Fiat is looking to work on a joint venture with with Chrysler to produce large SUVs at Mirafiori for the Jeep and Alfa Romeo brands, but it absolutely needs its labour groups on side.

The automaker says it needs a specific collective agreement for this new JV to work, noting the clock is ticking. In fact, Marchionne's spokesman spelt it out in stark terms to just-auto - the timetable is just two months.

"There are industrial deadlines and investments that need to be put in place as soon as possible," is Marchionne's view.

Word is that three more moderate unions are ready to put pen to paper and sign some sort of deal that will secure the EUR1bn (US$1.31bn) investment in Mirafiori and the possibility of creating new jobs.

Marchionne never mentions Fiom by name. But the union is the one that has constantly proved a fly in the ointment for the manufacturer. The Fiat boss has now set the deadline, is it enough time to swing the unions on board?