Taro Aso, Japan's defeated prime minister, has officially resigned the leadership of his party following its trashing in Sunday's general election.

"I find it quite unfortunate that I've lost quite a few colleagues, and as party head, I feel this responsibility quite heavily," he told a news conference on Monday at the headquarters of his Liberal Democratic Party (LDP).

"For the LDP, I feel that we should have a new party leader election and aim for a new start," he added.

The party picked Taro Aso as its fourth leader in four years, hoping he would turn around its sagging fortunes and preserve its grip on power.

"I have no plan to run for re-election," Aso said, adding that "the most important thing is rejuvenating our party."

His successor is expected to be named late next month.

Although voters gave the Democratic Party of Japan (DPJ) a landslide win, most voters were seen as venting dissatisfaction with the LDP and the political status quo more than they were endorsing the policies of the untested opposition.

The LDP have governed Japan for virtually all of the past 54 years, barring a short break in the early 1990s.

But many voters saw the conservative, pro-business party as out of touch and ineffective in its handling of Japan's worst recession since the Second World War.

Aso himself was also seen as a liability after a series of policy flip-flops and gaffes ravaged his approval ratings, sparking turmoil in the LDP and alienating voters.