Fiat has frozen a EUR500m investment into its Officine Automobilistiche Grugliasco (formerly Corrozzeria Bertone) plant in Turin due to the refusal of one out of its four unions to agree terms.

The Italian automaker’s decision to temporarily withdraw its investment – the bulk of which was due to be ploughed into Maserati production – came after main union FIOM pulled out of talks to discuss the issue internally.

Fiat was looking for FIOM to accept a deal based on productivity improvements similar to those finally agreed at its nearby Mirafiori plant, but the union declined.

“We are requesting the same agreement we have in place at Mirafiori up the road,” a Fiat spokesman told just-auto. “FIOM refused to agree of course.

“Because FIOM membership is the majority at that plant, negotiations yesterday stalled. We can’t push ahead with just the approval of the other three unions. Given the current situation our plans for the plant are frozen for the time being.”

Should the EUR500m cash injection go ahead, Fiat estimates it could produce 50,000 Maserati vehicles annually at the plant.

FIOM’s hardline stance is the latest skirmish in many on-going battles the labour body has had with Fiat.

The automaker is attempting to introduce sweeping industrial relations changes as part of its Fabbrica Italia restructuring and investment plan.