TOKYO - JAPAN'S Prime Minister Taro Aso survived a no-confidence motion by an emboldened opposition in parliament on Tuesday but acknowledged his long-ruling conservative party faces a tough battle in national elections next month.

Aso's Liberal Democratic Party, which has ruled Japan for virtually all of the past 50 years, easily defeated the no-confidence motion submitted by the opposition bloc because along with its coalition partner the party controls the lower house of Japan's parliament.

But the motion gave the opposition, led by the Democratic Party of Japan, an opportunity to further embarrass the leader and heap criticism on Aso's economic policies and alleged lack of direction amid one of the country's worst economic downturns in decades.

Polls suggest Aso's party could lose when the parliamentary elections are held on Aug. 30. Aso, whose support is around 20 per cent, announced the election date after his party suffered a major upset in polls for seats in Tokyo's municipal assembly over the weekend.

'I humbly accept criticism of our loss in the local elections,' Aso told lawmakers. 'We have to win this election by all means. We must continue implementing economic measures. It is our responsibility to the public.'

Aso had to call the national elections by October - when the current roster's terms end - and had resisted calling them earlier.

But he apparently decided to push ahead with them because of mounting pressure from the opposition, voters and members of his own party who want him ousted.

The leader of the party that wins next month will almost certainly become Japan's next prime minister. -- AP