On the eve of a G8 summit due to address climate change, Britain admitted on Wednesday that it, and by implication others, has been drastically understating its true carbon emissions.

The government, which boasts of its success in curbing national emissions of climate warming carbon, said the real picture was reversed if carbon linked to imported goods was included.

"Under international climate change agreements, we only have direct influence over our domestic emissions - and they are, and will remain, the basis for these commitments," said environment minister Hilary Benn.

"But as we accelerate the move to a low-carbon economy, we must help business and individuals to understand and reduce the environmental impacts of the products and services they produce, sell or consume, wherever in the world they are made."

The new report from Benn's ministry said emissions of carbon dioxide (CO2), the main climate culprit, fell by 5 percent between 1992 and 2004.

But it said they actually rose by 115 million tonnes or 18 percent over the same period when the carbon emissions linked to imported goods were included in the calculation.

The report echoes studies last year by the Tyndall Centre for Climate Change Research and the New Economics Foundation think-tanks, which warned that governments were massively underestimating their carbon output by failing to count imports.

They noted that up to one-quarter of China's carbon emissions were due directly to its export trade to Europe and the United States after they effectively sent their smokestack industries there in the 1990s.

The G8 summit in Hokkaido and the larger Major Economies Meeting on its fringes are aimed at boosting efforts for a new global climate change treaty next year.

But negotiations ahead of the July 7-9 summit have been bogged down in arguments between developed and developing countries over who should take the first steps.

"If we are going to tackle climate change and create a strong low-carbon economy, emissions must be reduced in the UK and internationally," said Benn.

"That's why we are working to secure a comprehensive, long-term global climate deal that involves all the world's major economies, that puts us on track to cut global emissions in half by 2050."

Britain insists that the developed world take the lead in cutting emissions of carbon, which scientists say will boost global average temperatures by 1.8 to 4.0 degrees Celsius this century.

The United States, which rejected the previous Kyoto climate change pact, has agreed the developed world should lead but insists major emitters China and India must also take action.