"We are twice as worried about a potential FCA-PSA tie-up as we were about a merger with Nissan-Renault on the future of FCA's Italian factories" Michele De Palma, head of the auto sector workers at FIOM, told Reuters.

Fiat Chrysler and France's Peugeot confirmed on Wednesday they are in talks over a potential $50 billion (£39 billion) tie-up.

(Reporting by Francesca Piscioneri, editing by Silvia Aloisi)