Five-time Ballon d'Or victor Ronaldo completed a £100million move from Real Madrid to the Serie A champions on Tuesday, becoming their record signing.
That holding company, Exor, owns 64 per cent of Juventus, and 30 per cent of Fiat Chrysler Automobiles (FCA).
For the USB union, the decision means Fiat is missing out on investment.
The USB union said that the £99 million required to sign the 33-year-old player to Juventus should have been invested to safeguard the future of Fiat's future of thousands of people, "rather than enriching only one". "The company should invest in auto models that guarantee the futures of thousands of people, rather than enriching only one".
"It's a pleasure for me and everyone to play with someone like Ronaldo, the best in the world", Cancelo said at his presentation Press conference.
Liverpool FC finished in fourth place in the Premier League table last season as they secured Champions League qualification for next season.
The France worldwide has starred at the World Cup in Russian Federation but was heavily criticised for his performance last term and has struggled to flourish in Mourinho's defensive system.
After nine years, four Champions League crowns and two La Liga titles with Real Madrid, Ronaldo completed a surprise move to Italy's Serie A earlier this week, saying "the time has come to open a new stage in my life".