Yara, created by the spin-off of Norsk Hydro's fertiliser business, said Russian rivals got an unfair subsidy from cheap gas. With lobby group the European Fertiliser Manufacturers Association, it is pressing the EU to insist on price rises.
"We are afraid that we will be in a situation where the EU demands will be as soft as cake," said Willem van der Weiden, vice president of Yara Belgium, adding that gas accounted for about 80 percent of the cost of fertiliser production.
"We don't want to let our house be ruined again by capacity that is illegally dumped," he told Reuters, referring to tough restructuring in the past of the European fertiliser industry.
Russia is the world's largest producer of gas and sells it to domestic industry and household users at prices well below those in the European Union - leading to complaints that Moscow is giving its manufacturers an unfair competitive advantage.
The European Commission, which negotiates trade on behalf of the 25-nation EU, has pressed Russia to raise gas prices for industry as part of Moscow's efforts to get into the WTO.
But Moscow insists these lower prices are due to a natural competitive advantage as the gas is cheap to produce. Russia must negotiate trade deals with all its main partners, including the EU and the United States, before entering the WTO.
Yara and the EU fertiliser lobby group said they feared the EU would relax its demands, for the sake of getting a deal at an EU-Russia summit on May 21.
European Fertiliser Manufacturers Association head Helmut Aldinger said gas was being supplied to Russian fertiliser firms at a price three to four times lower than the export price.
His association wants the EU to get Russia to agree to a phased rise in gas prices to around $50 per thousand cubic metres within one year of accession to the WTO from the current level of around $30. Two years after accession, the price should rise further, to around $60 per thousand cubic metres, it said.
"Russian firms would not collapse, but it would avoid the predatory effect they have on Western industry," Aldinger said.