Japan's defeated Democratic Party of Japan (DPJ) on Tuesday picked as its new leader the industry minister during last year's Fukushima nuclear crisis, after suffering a landslide electoral defeat.

Banri Kaieda, 63, who broke down in tears in parliament last year as he faced heavy criticism over his handling of the accident, notched up 90 of 144 votes from party members, beating Sumio Mabuchi, a 52-year-old former infrastructure and transport minister.

"I will do my best to reconstruct the DPJ. Please give me your support," Kaieda told fellow lawmakers after being chosen as party president.

Tuesday's vote was largely a sideshow in the runup to the installation on Wednesday of Shinzo Abe as Japan's new premier.

The centre-left DPJ suffered a crushing defeat at the hands of Abe's Liberal Democratic Party in a general election earlier this month, seeing its representation in the powerful 480-seat lower house of parliament dive by about three-quarters to 57 seats.

The conservative LDP's landslide win ended three years of DPJ rule, with outgoing Prime Minister Yoshihiko Noda saying he would resign from the party's top job in the wake of the defeat.

Analysts said it could take years for the DPJ to retake power as urban voter support fell away, while some swing voters put their backing behind a new party led by conservative former Tokyo governor Shintaro Ishihara and reformist Osaka mayor Toru Hashimoto.

The DPJ's 2009 election win was historic for the country's staid political scene, which had seen almost unbroken LDP leadership for the past five decades.

Key to the defeated party's chances of regaining power would be bringing "leftist forces" together to differentiate it from Abe's conservative LDP, said Shigeki Uno, professor of political thought at Tokyo University.

In a speech before Tuesday's vote, Kaieda said the party was "necessary for Japan today and tomorrow".

"The DPJ has two great roles. One is the role as a party which pursues social equity," he added.

"The other role is the DPJ as a reformist party. We have forgotten that we are a reformist party, haven't we?"

Kaieda was trade and industry minister in 2011 when Japan was hit by a massive earthquake and tsunami that sparked the disaster at Fukushima, the world's nuclear accident since Chernobyl.

After facing a barrage of criticism over his handling of the affair, Kaieda broke down in tears in parliament, a rare episode for a Japanese politician.

On foreign policy, Kaieda is seen as pro-China and has said that he does not see Beijing's growing military might as a threat to Japan.

Tokyo and Beijing are embroiled in a diplomatic row that flared in September when Tokyo nationalised a group of East China Sea islands at the centre of the sovereignty dispute.

Kaieda is a free trade advocate who recently backed off that position, which is deeply unpopular among Japan's powerful and highly protected farm lobby.