TOKYO (AFP) - Japan's Opposition slapped a censure motion on embattled PM Taro Aso Tuesday as his party sank deeper into crisis ahead of a general election that it appears likely to lose. The censure in the Opposition-led upper house carries no legal force but is another embarrassing rebuke for Aso, whose party risks being swept from power next month after half a century of almost unbroken rule. "I take it earnestly," Aso told reporters, adding however that he was "quite dissatisfied" that the motion had delayed a debate on key issues in parliament. The Opposition accused the 68-year-old Premier of being unfit to lead the nation, criticising him for policy flip-flops and wasteful economic stimulus measures aimed at wooing voters ahead of the August 30 election. "The Aso government has failed to produce any result on the economy or other measures and is only clinging onto power," said Yukio Hatoyama, leader of the main opposition Democratic Party of Japan (DPJ). Next month's vote "will be a day when the history of Japan changes", he told party members. "Let's join forces in grabbing power." The Opposition also introduced a no-confidence motion against Aso's cabinet in the more powerful lower house, but it was shot down by the ruling Liberal Democratic Party (LDP). The Premier thanked the government and ruling party for "acting as one" to defeat the motion, "despite differences in opinion". Aso's LDP has a comfortable majority in the lower house, thanks to a resounding win under popular premier Junichiro Koizumi four years ago. The ruling party argues that the DPJ, which has never been in power, lacks the experience to run the world's second largest economy. "What people want is the capability to manage a government," LDP Secretary-General Hiroyuki Hosoda said in parliament. But voter surveys suggest Aso's party is likely to be beaten in next month's polls by the DPJ, which won control of the upper house in 2007. Aso's growing woes come despite recent signs of an improvement in the economy, which has slumped to its worst recession since World War II due to a collapse in exports triggered by the global economic downturn. The beleaguered Premier, a former diamond trader and one-time Olympic marksman, has unveiled a series of stimulus spending packages, including cash handouts for households. A victory by the DPJ in the lower house election would bring an end to almost two years of legislative deadlock in Japan, which has had three prime ministers since the reform-minded Koizumi stepped down in 2006. The LDP has been in open disarray in recent months, with some of Aso's own lawmakers calling for a change of leadership. A veteran LDP lawmaker, Hajime Funada, said Monday it would be "suicidal" for the party to continue under Aso while a junior LDP politician, Yukari Sato, also called for a new leader. Aso, however, has vowed to fight on, saying it would be "irresponsible" for him to abandon the job. "It's a crucial time when I must hold on by clenching my teeth," he told reporters late Monday. His approval ratings have sunk below 20 per cent in recent surveys as voters turn to an opposition promising a more inclusive society and a middle road between a welfare state and a free market system. The DPJ scored a victory Sunday in a local poll seen as a bellwether of the national polls, taking 54 seats in the Tokyo assembly, where it became the largest party for the first time. LDP won 38 seats while its coalition partner New Komeito took 23, leaving the ruling bloc three seats short of the 64 needed for a majority. The remaining 12 seats went to other opposition and independent candidates.