Japan was struck by a political tsunami yesterday as the Liberal Democratic Party (LDP) was swept aside after 54 years of virtually unbroken conservative rule.

Several generations of political careers, including those of at least one former Prime Minister, were brought to a humiliating end as the centrist Democratic Party of Japan (DPJ) won a crushing victory.

It was the country’s most decisive election result, and the DPJ’s victory puts Japan in the hands of a party in which the young, women, and trades unions have greater power than at any time before.

“I believe that everyone felt great rage towards the Government,” said Yukio Hatoyama, the DPJ’s leader, who is now certain to become the next Prime Minister. “Everyone was convinced that there had to be a change. The DPJ will form the Government but we will not be arrogant and we will lead according to the will of the people.”

By the early hours of this morning the DPJ was heading towards a total representation of about 310 seats in the lower house of the Diet, compared with about 120 for the LDP. The result will allow the Democrats to dominate the new parliament and to push through their agenda of increased welfare spending, reduced public works, friendlier relations with China and a more detached and independent relationship with the United States.

The vote has also eviscerated the LDP, one of the world’s longest-reigning democratic political parties, and the institution that claims credit for Japan’s recovery from a defeated nation after the war to an economic superpower. “It is very severe but it is the judgment of the people,” said Taro Aso, the outgoing Prime Minister, who announced that he will resign as the party’s leader.

“From the beginning we knew this would be a difficult election but we must reflect [on this result] sincerely.”

Some of Japan’s most powerful and experienced LDP politicians lost their seats, often to DPJ candidates with little experience who were decades their junior. They included Toshiki Kaifu, 78, the former Prime Minister, and Shoichi Nakagawa, a former Finance Minister, who disgraced himself last February after appearing drunk at a press conference in Rome.His successor as Finance Minister, Kaoru Yosano, lost his Tokyo seat to his DPJ opponent.

Fumio Kyuma, 68, a former Defence Minister, was defeated in his Nagasaki constituency by Eriko Fukuda, a 28-year-old woman who came to prominence after accidentally contracting hepatitis C from a blood transfusion. Those who lost their constituencies, however, may be given some of the 180 seats in the Diet that are allocated by proportional representation.

Opinion polls had predicted an overwhelming victory for the DPJ but it was still a day of high excitement as the political tables were turned for the first time since the LDP’s foundation in 1955.

The party briefly lost power in 1993 but the coalition of smaller opposition parties who governed in its stead for less than a year never enjoyed a mandate as powerful as the one handed yesterday to the DPJ.

As the extent of the rout became evident, Japanese television broadcast live from the election headquarters of DPJ candidates, who celebrated their victories with the traditional raised arm salutes and cries of “Banzai!” (may you live 10,000 years).

Yesterday’s result was as much an expression of disgust with the weak leadership and complacency of the LDP as a positive vote for the DPJ. But in contrast to previous elections Mr Hatoyama and his party have succeeded in articulating a distinctive platform, which, if it can be put into effect, will mark a clear break from the politics of the postwar era.

The DPJ promises free secondary education, free treatment and delivery for expectant mothers, and an annual allowance of 312,000 yen (£2,000) to all children until they leave junior school.

Mr Hatoyama proposes to cover the cost of this vast spending — Y16.8 trillion in 2013 — without immediately raising taxes. He will cut spending on dams, roads and public projects such as a museum of popular culture, the personal project of Mr Aso.

Once in power the DPJ promises to put more MPs into junior jobs in ministries and to establish a national strategy bureau — something like the No 10 Policy Unit — to curb the power of the bureaucracy.

There will be a crackdown on the practice known as amakudari — “descent from the heavens” — whereby retiring civil servants secure jobs in the industries that they formerly supervised. To the alarm of some US commentators Mr Hatoyama has taken an outspoken stand against unfettered international capitalism, promising to abandon the country’s “worship” of the US and to break away from decades of unquestioning support for American foreign policy.

“Japan now needs to make a clear shift from diplomacy that follows the US lead, to diplomacy based on multilateral co-operation,” he said earlier this year. “We must view the AsiaPacific region, where we have increasingly close ties with other countries, as the place where Japan will live as a nation.”

The LDP’s appeal to voters was based principally on apologising for its own mistakes and scaremongering about the inexperience and brittleness of its opponents. In the past the DPJ has, indeed, appeared divided and Mr Hatoyama’s first task will be to announce a Cabinet that balances its various interest groups — including conservative former LDP members, trades union-backed ex-socialists and Ichiro Ozawa, the party’s most experienced and feared politician who commands his own powerful faction.

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