"The decision by FCA and PSA to start negotiations to merge the two groups without any involvement of, or communication to workers and union representatives is unacceptable," France's CGT and Italy's Fiom-Cgil unions said in a joint statement.

Fiat Chrysler and PSA on Thursday announced a plan to join forces in a 50-50 share merger to create the world's fourth-largest automaker, seeking scale to cope with costly new technologies and slowing global demand.

As things stand, the deal would produce positive results just for the two companies' investors and financial markets, CGT and FIOM said. The two labour groups said they would work together to safeguard jobs as well as research, development and production capacity in Europe.

(Reporting by Silvia Aloisi; editing by James Mackenzie)

Stocks treated in this article : Peugeot, Fiat Chrysler Automobiles