Only five out of around 1,700 workers expected for Monday's shift at a Fiat Chrysler plant in Italy participated in a strike to protest Juventus' signing of Cristiano Ronaldo, a spokesman for the carmaker said.

"The protest actions promoted in recent days over football were a resounding flop," the Fiat spokesman said.

USB, a small and independent union, were protesting over the €100 million Juventus spent to sign Ronaldo. The Agnelli family that own as 63.77 percent of the Serie A champions also own 29.1 percent of Fiat, and reports earlier this month said the carmaker could help the club subsidise Ronaldo's salary.

The original call to strike had protested that the owners were spending such vast amounts of money on a footballer, while workers were forced to make sacrifices merely to survive, with the car manufacturer having already reneged on several promises to improve conditions.

But the Fiat spokesman said the participation rate of 0.3 percent at the plant in Melfi showed the strike was promoted by groups that were not representing the workforce.

Unions representing the majority of FCA workers had rejected the strike, which was supposed to take place between late Sunday and early Tuesday, calling it "mere advertising."

Ronaldo, the global superstar who completed his move from Real Madrid last Tuesday, underwent his medical exam with Juventus on Monday ahead of his official unveiling.