Japan reported its biggest half-year trade deficit ever as exports weakened and fuel imports soared to keep the power on while most reactors are idled in the aftermath of last year's nuclear crisis.

The Ministry of Finance on Wednesday reported a 2.9 trillion yen ($47.8 billion) trade deficit for the first half ended June 30. The deficit was triple the size of the deficit reported for the same period last year. First half exports fell 2.5 per cent from last year while imports surged 13.1 per cent.

The latest trade deficit is the biggest since Japan started compiling such records in 1979.

Until this month, all 50 of Japan's working nuclear reactors were offline after the nuclear crisis set off in March 2011 by a massive earthquake and tsunami. Two reactors are now back online but the country still must rely more on oil and gas to supply electricity.

Exports were dented by weaker demand stemming from Europe's debt crisis. A strong yen also hurt exports.

Disruptions to parts supplies caused by the disaster in northeastern Japan have also hurt exports as production of autos and electronics slowed, although have since recovered.

Imports surged on the back of the growing cost of importing fuel, including oil, petroleum products, gas and coal.

Japan has managed to eke out small trade surpluses in some months over the last year.

Earlier this year, Japan reported a record annual trade deficit for the fiscal year ended March.

- AP