TOKYO - Political leaders took to the streets Tuesday as campaigning kicked off in one of the most hotly contested elections Japan has seen in more than a decade, a race in which the party that has ruled the country for most of the past 55 years is considered a distant underdog.

The elections for the lower house of parliament, to be held Aug. 30, will be a big test of Japan's ruling Liberal Democratic Party and could cost them control over the government and lead to the selection of opposition chief Yukio Hatoyama as Japan's next prime minister.

The Liberal Democrats have governed Japan alone or in a coalition arrangement for all of the past 55 years, except for a 10-month respite in the early 1990s.

"We will press ahead," Prime Minister Taro Aso said in his kickoff speech before a swarm of voters who braved the summer sun in a Tokyo neighbourhood. "We are not finished with our efforts to see economic recovery. Recovery is our foremost priority."

Hatoyama, head of the Democratic Party of Japan, called for change.

"The day has come to change the history of Japan," Hatoyama said on a campaign tour in the western city of Osaka. "Let's step into a new era with courage."

The ruling party has been plunging in support because of the weak economy, increasing unemployment, a perceived lack of leadership and its support of higher taxes. Aso, who is party president, is also deeply unpopular for his failure to lead the country out of its troubles and his tendency to make embarrassing gaffes.

In a poll released Tuesday by the Asahi, one of Japan's most influential dailies, Aso's support rating was 19 per cent, while his disapproval rating was 65 per cent.

The poll said the ruling party has 21 per cent support among voters, compared with 40 per cent who say they will opt for the Democratic Party of Japan. It said 27 per cent were undecided.

The Asahi poll of 1,011 voters was in line with other recent polls by major media. A poll of that size would normally have a margin of error of about five percentage points.

"The latest poll by the Asahi newspaper is a clear indicator that Aso's Liberal Democratic Party is in deep trouble with voters," said Hiroshi Kawahara, a professor of Japanese politics at Tokyo's Waseda University. "Voters are frustrated with the party's economic and welfare policies, and the poll showed they want a major change in government."

Aso and opposition leader Hatoyama have squared off twice in televised debates ahead of the official start of campaigning.

Aso has stressed that his party has delivered results and built up the country from the ashes of defeat in the Second World War in 1945, while alleging that the opposition is making promises of public spending and social programs that it cannot pay for.

Hatoyama, meanwhile, has said Japan needs a change of government to get itself out of its current morass, that it must cut wasteful spending, reduce oil taxes and highway tolls, and rein in the power of bureaucrats, who have broad authority over setting budgets and formulating laws.

Hatoyama has also vowed to make Japan's foreign policy less dependent on Washington, its main military ally and trading partner.

The elections are for the 480 seats in the lower house, the more powerful chamber of Japan's bicameral parliament. Going into the vote, the Liberal Democrats had a commanding 302 seats, and the Democratic Party had 112.

The Democratic Party, founded 10 years ago, has controlled the upper house since elections in 2007, but the party that controls the lower house has the power to install the prime minister.