Aso asked his close ally Nakagawa to stay in his post on Monday, but pressure for the minister to resign emerged from within his own Liberal Democratic Party (LDP).

Emboldened opposition parties had been set to grill Nakagawa again in parliament and have said they would submit a censure motion to the upper house if his answers fail to satisfy.

A censure is non-binding, but a previous cabinet minister quit after a similar resolution.

The fuss over Nakagawa's behaviour at the G7 news conference comes as Aso's public support is plummeting -- below 10 percent in one survey published on Sunday -- ahead of the election.

Media polls show the main opposition Democratic Party of Japan has a good shot at ousting Aso's Liberal Democrats, ending more than 50 years of almost unbroken rule.

One budget-related bill is stuck in the opposition controlled upper house while the budget for the 2009/10 fiscal year, which starts on April 1, is being debated in the lower house.

Annual budgets typically are enacted by the end of March but this year's could be stalled by the political fuss.