Tokyo stepped up its rhetoric about the possibility of imminent foreign currency intervention as the yen hovered close to a four-and-a-half year high against the dollar, threatening the competitiveness of Japan's exporters.

Speaking on the fringes of the Group of 20 meeting in Berlin, Hiroshi Watanabe, vice-finance minister, said: "The movement in currencies in the past seven days has been rapid and erratic, meaning this is the proper time to think of intervention."