France's CGT union has called for more transparency at Renault and its Dutch holding company and asked the French government, one of the carmaker's shareholders, to try to shed light on its workings, a CGT representative said Thursday.

Renault, and its alliance with Nissan Motor Co., has been in the spotlight after the partnership's architect, Carlos Ghosn, was arrested in mid-November in Japan amid allegations his Nissan income was understated.

The CGT wrote to French Economy Minister Bruno Le Maire in early December questioning the way Renault had handled the affair and to denounce a lack of transparency at RNBV, a joint Renault-Nissan holding company based in the Netherlands, FranceInfo reported Thursday.

A CGT spokesman confirmed the union had reached out to Le Maire and to Renault's deputy CEO, Thierry Bollore, adding it was calling for clarity on additional wage payments made via RNBV to an unidentified member of the French carmaker's executive committee.

"Workers have no information about RNBV," the CGT spokesman said.

Spokesmen for Le Maire and for Renault declined comment. The French government owns 15 percent of Renault.

Executives from both carmakers in the Renault-Nissan alliance looked at least twice at legal ways to pay Ghosn undisclosed income through the partners' shared finances, including via RNBV, it was reported earlier in December.

The two efforts discussed were ultimately abandoned.

Ghosn, who remains Renault's chairman and chief executive but was ousted as Nissan's chairman, has been in a Tokyo jail since mid-November.

He had been expected to possibly go free on bail last Friday but was re-arrested by prosecutors on new allegations of making Nissan shoulder $16.6 million in personal investment losses.