Japan's finance minister announced Tuesday he will step down because of health problems after facing allegations he was drunk at a recent summit meeting, dealing a major blow to Prime Minister Taro Aso's already shaky government.

Finance Minister Shoichi Nakagawa, who has denied being drunk, said he will stay on until parliament approves a supplementary budget, probably in April.

"I apologize for causing such a big fuss," Nakagawa said. "I plan to submit a formal resignation as soon the budget and related legislation are passed by the lower house."

Nakagawa has been under fire over allegations he appeared to be drunk at a news conference following the G-7 finance ministers meeting in Rome over the weekend. TV footage showed him slurring his speech and looking drowsy and confused.

Nakagawa has denied he was drunk, saying he had taken cold medicine, which, along with the jet lag, made him groggy.

His abrupt resignation announcement was seen as an attempt at damage control. Opposition lawmakers were already planning to submit a censure motion against him and demand he quit.

Aso had told reporters he had no plans to sack the minister, and urged Nakagawa to rest well and stay on. But pressure for Nakagawa's resignation was growing within the cabinet.

"The TV footage was shocking," Consumer Minister Seiko Noda said. "A cabinet minister must be fit and he needs more self control."

The scandal was the latest in a series of embarrassments that have plagued Aso, who has been in office only since late September.

Aso's support ratings fell into the single digits in a recent poll, and calls are growing for him to step down and call snap elections.

Opposition leaders said Nakagawa's announcement does not affect their plans to submit the censure motion, and also slammed Aso for choosing Nakagawa.

"I don't understand why he has to wait until the budget approval," said Higashi Koshiishi, a leader of the main opposition Democratic Party of Japan. "And we will by all means question Prime Minister Aso's responsibility over [Nakagawa's] appointment."

The censure motion was certain to be endorsed in the opposition-dominated upper chamber and would further embarrass Nakagawa and Aso, though the vote is non-binding.

Plunging popularity and the Nakagawa scandal have increased speculation Aso's days might be numbered. Elections must be held by the end of September, but can be called at any time.

Several polls suggest that the opposition has a good shot at winning if elections are held soon. The Liberal Democrats have controlled the government for virtually all of the past 54 years.