"They are not in fact saying we should join the euro tomorrow," Blair said, reporting back to parliament after the annual summit of the heads of the world's top industrial nations, which took place on the Japanese island of Okinawa.

"For Japanese inward investors the important thing is that the decision on the euro is taken on economic grounds," he said.

"What they are saying is when that decision is taken they want as investors in our economy to know that we have the interests of the British economy, British jobs and industry and investment as the highest priority for our decision."

At the G8 summit, Blair reassured Japanese Prime Minister Yoshiro Mori on Thursday that Britain was committed to joining the European single currency if the conditions were right.

Japanese manufacturers with plants in Britain, hit hard by the pound's strength, have grown increasingly impatient with what they see as Blair's prevarication over the single currency. Japanese car manufacturers have made it plain they would welcome the stability that an early decision to swap sterling for the euro would bring. Toyota Motor Corp, Japan's biggest carmaker, said last week it planned to buy fewer parts in Britain and increase purchases of components made by continental European companies because of the strong pound.

Aides said Blair would meet chiefs from Nissan Motor Co, Japan's third-biggest automaker, next week for talks about the future of its plant in Sunderland, northeast England. Nissan has said the strong pound could divert investment from the plant to elsewhere in Europe.