After 54 years of nearly unbroken rule, Japan's ruling conservative party conceded defeat Sunday to the left-of-centre opposition in parliamentary elections.

Yukio Hatoyama, leader of Japan's main opposition Democratic Party of Japan, stands in front of a white board full of red rosettes attached on victorious candidates' names after observing ballot counting. (David Guttenfelder/Associated Press)

Preliminary results broadcast by Japanese TV networks show the Democratic Party of Japan (DPJ) is poised to capture 300 of 480 lower house seats — more than enough to control the national agenda — ousting the Liberal Democrats, who have governed Japan for all but 11 months since 1955.

Official results are expected early Monday.

Prime Minister Taro Aso said he takes responsibility for the defeat and will resign as head of the Liberal Democratic Party (LDP).

"These results are very severe," he said at party headquarters in Tokyo. "There has been a deep dissatisfaction with our party."

Kotaro Tamura, an LDP member of the national legislature, said his party made too many "crucial mistakes," including changing the prime minister three times without holding an election.

The untested DPJ has promised to boost spending on social programs and reduce the power of bureaucrats.

Prime Minister Taro Aso listens to a TV interview while observing the result of parliamentary elections ballot counting at the party headquarters in Tokyo. (Shizuo Kambayashi/ Associated Press)

The opposition's win comes as Japan struggles with record unemployment and an economy that is showing tentative signs of emerging from a bruising recession.

DPJ leader Yukio Hatoyama, the apparent new prime minister-in-waiting, said voters were "angry with politics and the ruling coalition." During the campaign, the party accused the government of ruining Japan's social security net and widening the gap between the rich and poor.

"We felt a great sense of people wanting change for their livelihoods and we fought this election for a change in government," he said.

As opposition leader, Hatoyama, 62, was a strong critic of what he called Tokyo's subservient position to Washington.

With his party now expected to take power, he is expected to strengthen economic ties with Japan's Asian neighbours, including China. Japan should work with other Asian countries to create a single regional currency, Hatoyama wrote in an op-ed piece for The New York Times last week.

He said he would not seek radical change in Japan's foreign policy — that the U.S.-Japan alliance would continue to be the cornerstone of Japanese diplomatic policy — but he predicted "the era of U.S.-led globalism is coming to an end."

With files from The Associated Press