Some of the biggest US hedge fund investors have made billions betting against the yen, exploiting Japan's determination to weaken its currency and boost its economy.

Wagering against the yen has emerged as the hottest trade on Wall Street over the past three months. George Soros, who made a fortune shorting the British pound in the 1990s, has scored gains of almost $1bn on the trade since November, according to people with knowledge of the firm's positions. Others reaping big trading profits by riding the yen down include David Einhorn's Greenlight Capital, Daniel Loeb's Third Point and Kyle Bass's Hayman Capital Management, investors say.