Fears were growing today that the price of natural gas could rise sharply after the world's biggest suppliers agreed a charter which could see them form a cartel as powerful as the oil exporters' Opec.

The 15-strong Gas Exporting Countries Forum refused to reveal details of its charter, which was signed off in Moscow. But Sergei Shmatko, Russia's energy minister, made it clear the countries had agreed to consult each other to prevent providing too much gas, pushing prices down.

"We finally created a full-blown international organisation with very ambitious and outstanding goals," he said. "Avoiding the creation of an unnecessary oversupply of gas in one region or another, which would undoubtedly end up putting pressure on prices, is of paramount importance."

The world gas market is far less organised than the oil market. About 70% of output is sold and distributed locally through pipelines, and pricing tends to be on a local rather than international basis. However, a growing part of gas trading is in liquefied natural gas, which can be transported by tanker.

Venezuelan energy minister Rafael Ramirez told the Moscow meeting the gas producers should adopt the same principles as Opec, adding: "We need mechanisms and tools that will let us better interact between gas exporters to avoid competition."

Russia is the largest gas producer in the world followed by Iran, Algeria and Qatar. Last night's meeting decided that the forum's new headquarters will be in Doha, Qatar, despite an offer by Russian Prime Minister Vladimir Putin to fund an HQ in St Petersburg.

Putin tried to play down fears from Western consumer countries that the new organisation will push up gas prices. He said any rises should not be based on cartel agreement but on the increasing costs of exploring and extracting natural gas as producers move into more hostile environments to find new supplies.

Gas prices fell to their lowest for more than two years overnight, primarily reflecting the sinking oil price.

The UK is becoming more dependent on gas as its primary source of energy even though North Sea supplies are running out. That will make it even more dependent on the major exporters.