TOKYO – Chaos deepened on Wednesday in Japan's ruling party ahead of an expected August 30 election, as lawmakers fearing a crushing defeat persisted with efforts to ditch unpopular Prime Minister Taro Aso.

Opinion polls show the main opposition Democratic Party ahead of Aso's Liberal Democratic Party (LDP), raising the prospect of an end to more than half a century of almost unbroken rule by the business-friendly conservatives.

Finance Minister Kaoru Yosano, who has been critical of how Aso decided to call the election right after a huge LDP loss in a weekend Tokyo assembly poll, met the premier on Wednesday, although it was not clear what they discussed. Yosano was accompanied by Agriculture Minister Shigeru Ishiba.

Aso needs agreement from all cabinet members to call an election, but can fire any who refuse and go ahead with his plan.

A source close to Yosano said the finance minister had met the premier to explain how tough the Tokyo election had been, while Ishiba wanted to convey the grim situation in his own district.

Aso said on Monday he would dissolve the lower house next week for an August 30 election, a move critics in his party said was aimed at fending off efforts to oust him before the vote.

A general election must be held no later than October.

Anti-Aso LDP lawmakers were pressing for a meeting of party lawmakers from both houses of parliament at which some, at least, want to force the prime minister to quit, despite the fact that Japan has already had four LDP prime ministers in as many years.

Such a meeting must be held if one-third of the 384 party parliamentarians sign a petition calling for the gathering.

We know of more people who are willing to sign, so I think we'll manage (to get enough signatures) by the end of the day, LDP lawmaker Masaaki Taira told reporters.

A media survey released on Wednesday showed the Democrats slightly widening their lead over the LDP, while a majority of Japanese voters want a election sooner rather than later.

About 36 percent of respondents to the Yomiuri newspaper survey said they plan to vote for the Democrats, up 1 percentage point from the last survey, while 21 percent will vote for the LDP, down 4 points. Fifty-six percent wanted an earlier election.

Some 45 percent of respondents saw Democratic Party leader Yukio Hatoyama as more suited for the premiership, while 25 percent preferred Aso, the survey showed.

The Democrats are not without their own headaches, though, after Hatoyama apologized for the fact that some people listed as his political donors were already dead. (Reporting by Yoko Kubota, Yoko Nishikawa, Yuko Yoshikawa and Chisa Fujioka; Writing by Linda Sieg, Editing by Chris Gallagher)