Japanese Prime Minister Taro Aso's already shaky government was rocked on Tuesday by the sudden resignation of his finance minister over allegations he appeared drunk after a recent summit.

Finance Minister Shoichi Nakagawa, who has denied being drunk, offered his resignation late on Tuesday after earlier in the day saying he would stay on until after parliament approves a supplementary budget, probably in late April.

Nakagawa's resignation was accepted.

"I have resigned," Nakagawa said. "I decided that it would be better for the country if I quit."

The resignation was a huge embarrassment for Aso, who the day before had asked Nakagawa to stay on. Economy Minister Kaoru Yosano will assume Nakagawa's duties, Kyodo News agency reported.