Japan's current account surplus tumbled 43.9 percent to a 15-year low in 2011 as the nation logged a trade deficit due to lower exports and higher energy costs, government data showed Wednesday.

The surplus in the current account, the broadest measure of trade with the rest of the world, stood at 9.63 trillion yen ($125 billion) in 2011, the lowest level since 1996, the finance ministry said.

The figure was down 43.9 percent from 2010, the sharpest year-on-year decline since 1985.

The surplus in returns on overseas investment and other income expanded "but the balance of goods and services trade slipped into the red, reducing the surplus in the current account," the ministry said in a statement.

The traditionally export-led economy has shifted to more overseas production as shown by strong figures for earnings from overseas assets held by Japan. Those earnings rose by nearly 20 percent to 14.03 trillion yen.

Analysts say any systemic shift in Japan's current account numbers could threaten the country's ability to finance its large government budget deficits.

Earlier data from the ministry showed Japan suffered its first annual trade deficit in more than 30 years in 2011 after the March quake-tsunami and strong yen hit exports while high fuel costs pushed up import bills.

The current account surplus for December alone dropped 74.7 percent to 303.5 billion yen, decreasing year-on-year for the 10th straight month since the March earthquake and tsunami disasters.

The surplus was smaller than an average of 337.5 billion yen expected by economists surveyed by the Nikkei business daily.

The March disaster disrupted manufacturing supply chains across Japan, hampering exports.

It also knocked out cooling systems at a major nuclear power plant on the nation's east coast, sparking the world's worst atomic disaster in 25 years and sending confidence in the technology plummeting.

Japan is resource-poor and its fossil fuel imports have soared in the wake of the Fukushima nuclear crisis, with atomic power stations being taken offline and thermal fuel plants used to make up the difference.

In addition, the eurozone debt crisis has slowed the global economy and sent traders scurrying to the safety of the yen, driving up its value and reducing Japanese exporters' incomes.

The current account measures trade in goods, services, tourism and investment.

-- Dow Jones Newswires contributed to this article --