The rising demand for flat-screen televisions could have a greater impact on global warming than the world's largest coal-fired power stations, a leading environmental scientist warned yesterday.

Manufacturers use a greenhouse gas called nitrogen trifluoride to make the televisions, and as the sets have become more popular, annual production of the gas has risen to about 4,000 tonnes.

As a driver of global warming, nitrogen trifluoride is 17,000 times more potent than carbon dioxide, yet no one knows how much of it is being released into the atmosphere by the industry, said Michael Prather, director of the environment institute at the University of California, Irvine.

Prather's research reveals that production of the gas, which remains in the atmosphere for 550 years, is "exploding" and is expected to double by next year. Unlike common greenhouse gases such as carbon dioxide, sulphur hexafluoride (SF6) and perfluorocarbons (PFCs), emissions of the gas are not restricted by the Kyoto protocol or similar agreements.

Writing in the journal Geophysical Research Letters, Prather and a colleague, Juno Hsu, state that this year's production of the gas is equivalent to 67m tonnes of carbon dioxide, meaning it has "a potential greenhouse impact larger than that of the industrialised nations' emissions of PFCs or SF6, or even that of the world's largest coal-fired power plants".

While concerns have led Toshiba Matsushita Display Technology to avoid using the gas, Air Products, which produces it for the electronics industry, told New Scientist that very little nitrogen trifluoride is released into the atmosphere. But Prather argues that as the gas is not controlled in the same way as other greenhouse gases, companies may be careless with it.