Tokyo - Japan's new government was off to a bad start Sunday: just four days after starting work, Transport and Tourism Minister Nariaki Nakayama, 65, resigned because of controversial remarks he made, broadcaster NHK reported.

The same day he was elected prime minister by the Japanese parliament on Tuesday, Taro Aso named Nakayama to the post.

With his resignation, the conservative former education minister took full responsibility for a series of controversial remarks, the report said.

His missteps apparently included disparaging remarks about the country's largest teachers' union Nikkyoso, which he called a "cancerous tumour" that should be removed.

Nakayama had previously enraged Japan's aboriginal Ainu people when he described Japan as "ethnically homogenous."

He had also described opponents of the expansion of Tokyo's Narita international airport as "squeaky wheels."

Media reports said that Nakayama would be replaced by the former minister for administrative reform, Kazuyoshi Kaneko.

The Japanese media have said the resignation is a setback for the new prime minister.

Aso's ruling Liberal Democratic Party, which has been in power for more than 50 years, is in danger of a defeat in elections for the lower house of parliament, which he is expected to call soon.

Aso has an approval rating of less than 50 per cent as he takes up the premiership, lower than his predecessor, Yasuo Fukuda, when he took up office.

Former premier Fukuda abruptly resigned on September 1, less than a year after he assumed the post, citing the difficulties his government faced in passing any legislation with the opposition- controlled upper house, the House of Councillors.

The opposition gained control of the upper house in September 2007. (dpa)