TOKYO, JAPAN - SUPPORT for embattled Japanese Prime Minister Yasuo Fukuda's cabinet has plunged below 20 per cent, the lowest for a government in more than seven years, a poll showed on Friday.

Surveys said the opposition's popularity was mounting as Mr Fukuda's government comes under fire, particularly over a new medical insurance plan that has confused many elderly people.

The latest drop in support came after Fukuda, concerned about a budget shortfall, rammed through parliament bills to reimpose a petrol tax that had expired, under pressure from the opposition.

Approval for the Fukuda government plummeted to 19.8 per cent, with disapproval rising to 66.6 per cent, Kyodo News said in a poll taken Thursday and Friday.

The news agency said it was the first time a cabinet's approval rating had slipped below 20 per cent since the premiership of gaffe-prone Yoshiro Mori, who quit in April 2001 after a year in office.

The latest poll figures are below those of Mr Fukuda's immediate predecessor Shinzo Abe, who resigned in September after a series of scandals and an election defeat that gave the opposition control of one house of parliament.

The opposition has pledged to create a true two-party system in Japan, where Mr Fukuda's Liberal Democrats have been in power for all but 10 months since the party was created in 1955.

Mr Fukuda, a 71-year-old political veteran, had been seen by the Liberal Democrats as a safe pair of hands after Abe, a young conservative ideologue.

But the Asahi Shimbun found in its own survey that support for the main opposition Democratic Party had topped that for the Liberal Democrats for the first time since Mr Fukuda took office.

The opposition enjoyed growing popularity among women, who have traditionally shunned them, said the Asahi, which surveyed 998 people.

The Asahi found that 66 per cent of voters opposed the reimposition of the fuel tax, far outnumbering the 22 per cent who supported it.

But it said that voters were divided on whether the opposition should pass a motion seeking an early election.

Mr Fukuda has repeatedly ruled out calling snap polls, at least until Japan hosts the summit of the Group of Eight rich nations in September.

The government has faced particular criticism for introducing a new medical insurance plan in April deducting costs directly from pensions for those aged 75 or older.

Many older voters have voiced concern that they may pay more and find the system confusing.

Japan has one of the world's most rapidly ageing populations, raising concerns about how the government will pay for rising medical costs and pension benefits. -- AFP