Gaz de France has warned that its sales will be hit if the French government refuses to let it raise gas prices.
Gaz de France was part-privatised earlier this year
The utility giant said it faced a 250m euro ($299m; £169m) slide in revenues and earnings in the first three months of 2006 because of the price freeze.
Despite higher world energy prices, the French government has blocked Gaz de France from increasing its charges from 1 January.
Shares in the part-privatised firm were down almost 1.5% in Paris trade.
Gaz de France said delays to increases in its charges since November 2004 would cost it a total of 750m euros by the end of the first quarter of 2006, up from an expected drop of 500m by the end of the current year.
French brokerage Societe Generale said the government's ongoing block on any rise in tariffs had come "as a surprise".
"The government's refusal represents a serious setback for Gaz de France," Societe Generale said in a statement.
The French government began the controversial partial privatisation of Gaz de France in June, with the sale of a 22% stake in the company.
Gaz de France wants to improve its finances as it looks to head off the challenge from energy giants such as Germany's E.ON and the UK's Centrica.