(Reuters) -- Japan posted its biggest ever trade deficit in January, topping the previous record seen during the financial crisis in 2009, Ministry of Finance data showed Monday, underlining concerns that a persistent trade gap may undermine the country's ability to finance its debt.

The trade deficit stood at 1.475 trillion yen ($18.59 billion), against median market forecast for 1.468 trillion yen, marking a fourth straight month of deficit, as weak global demand and a strong yen hurt exports and robust fuel demand boosts imports.

Exports fell 9.3 percent from a year earlier, down for a fourth straight month. That compared with a 9.5 percent drop expected by economists, following an 8.0 percent decline in the year to December.

Imports rose 9.8 percent in January from a year earlier, against a 9.5 percent rise expected, on high oil costs and hefty demand for liquefied natural gas to make up for a loss of energy supply due to the nuclear power crisis triggered by last year's earthquake and tsunami.

Japan logged an annual trade deficit in 2011 for the first time in 31 years as the March disaster, a global slowdown and a strong yen dealt a blow to an export-reliant economy.

To view full tables, go to the MOF website at:

http://www.customs.go.jp/toukei/info/index_e.htm ($1 = 79.3600 Japanese yen)

(Reporting by Rie Ishiguro; Editing by Michael Watson)

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