In an emailed statement, the CGT called GDF Suez's offer, which the company announced Wednesday, a "capitulation."
"Indeed it amounts to a change of GDF Suez's economic model, which will oblige the company to recuperate market share on the European and international markets," the CGT said.
The CGT and other major French unions regularly follow up on their discontent with strike action and other protests. Workers' union representatives managed to delay the merger between Gaz de France and Suez last year, which many of them opposed on the grounds that it watered down state control of the country's main gas supplier.
GDF Suez's press service wasn't immediately available to comment