But the DPJ has its own challenges, with almost no experience of running the government and with members from all walks of political life, such as LDP, trade unions and former social democrats.

The DPJ has vowed to cut wasteful spending and revitalise Japan's economy by increasing household incomes and encouraging spending. But it has offered few details on how it would fulfill its promises.

Hatoyama said he plans to review the current government's record-high stimulus package. His party's manifesto promises to raise monthly child allowances, and to scrap both expressway tolls and gasoline taxes as part of its plan to stimulate consumer spending.

The DPJ also said it could secure funds for its proposed programmes by cutting public works projects and increasing domestic demand while at the same time holding off on a sales tax hike for the next four years.

It vowed to introduce a guaranteed minimum income for farmers, minimum pensions and tax breaks for small- and medium-sized enterprises.

But while Japan suffers a mounting national debt exceeding more than 160 percent of its gross domestic product, experts call the party's costly policies unrealistic. The LDP has called them a 'pipe dream' and said they would require 'magic' to be realised.

Political centrist Hatoyama has also said he wants a more mature relationship with the US, gaining a more self-assertive voice for Japan in the international community.

With East Asian neighbours, Hatoyama foresees improvements as he plans no visits to the controversial Yasukuni Shrine for Japan's war dead, such as those by previous Japanese prime ministers which drew angry protests especially from China and South Korea.