A prickly row between the scientific academies of Britain and America over the precise wording of their positions on climate change has come to light on the eve of the G8 summit.

Letters show that shortly after the scientific academies of the G8 group of nations, as well as those from China, Brazil and India, issued an "unprecedented statement" urging action on climate change, the presidents of the Royal Society and the US National Academy of Sciences argued over how the statement was presented.

Bruce Alberts, the president of the National Academy of Sciences (NAS), accused Lord May, the president of the Royal Society, of misinterpreting the work of the American academy and causing "considerable confusion" in the American media and to the Bush Administration.

The argument undermines the show of unity achieved by the world's leading scientific academies on June 7 when they released their statement on climate change.

The academies of Britain, France, Russia, Germany, America, Japan, Italy and Canada, along with those of Brazil, China and India, combined to demand that the G8 summit: "Acknowledge that the threat of climate change is clear and increasing."

The statement urged the world's most powerful governments to adopt cleaner technologies, launch an international study to set targets for reducing greenhouse gas and to "recognise that delayed action will increase the risk of adverse environmental effects and will likely incur a greater cost."

But the day after the statement was published with an accompanying press release, Dr Alberts wrote to Lord May from his office in Washington to complain about comments made by the peer when the statement was released.

Lord May referred to the findings of a study carried about the NAS in 1992 and said: "The current US policy on climate change is misguided. The Bush Administration has consistently refused to accept the advice of the US National Academy of Sciences."

Dr Alberts responded by writing to the Royal Society and telling Lord May: "Your statement is quite misleading."

He accused Lord May of presenting the findings of the NAS, and their exact recommendations on cutting greenhouse gases, in a way that "considerably changed our report's meaning and intent."

"As you must appreciate," the letter continued, "having your own misinterpretation of the US Academy work widely quoted in our press has caused considerable confusion, both at my Academy and in our government."

"By advertising our work in this way, you have in fact vitiated much of the careful work that went into preparing the actual G8 statement." Dr Alberts then warned that future collaborations between the academies could be at risk.

The following day, Lord May replied to Dr Alberts but rejected his accusations. Apologising for the difficulties that Dr Alberts described, Lord May insisted that his comments corresponded to the findings of the NAS.

"I can understand that the Academy may have received criticism for re-stating its position so clearly and so appropriately now. It is clear not a politically convenient message for the US Government," he wrote.

The Royal Society said today that there has been no further contact on the issue since the exchange of letters, but stressed that the argument turned on the phrasing of the press release that accompanied the statement on global warming rather than its substance.

Relations between the two academies may be improved by a change of personnel; Dr Alberts retired as the president of the NAS last week.

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