TOKYO (Reuters) - Japan's main opposition Liberal Democratic Party (LDP) saw its voter support slip, but still maintained a commanding lead against rivals, including the ruling Democratic Party, ahead of a December election, public opinion polls showed on Monday.

The Nikkei business daily survey said 25 percent of those polled said they would vote for the LDP in a lower house election on December 16, while 16 percent would vote for the Democratic Party of Japan (DPJ).

The LDP figure represented a loss of 2 percentage points from the previous Nikkei poll, while the DPJ gained 5 percentage points.

More significantly, poll figures showed the new Japan Restoration Party, led by Osaka Mayor Toru Hashimoto, earned 11 percent support and the Sunrise Party, led by nationalist ex-Tokyo Governor Shintaro Ishihara, stood at 4 percent.

A Kyodo news agency poll credited the Japan Restoration Party with 6.8 percent and Sunrise with 1.0 percent.

Over the weekend, the two new parties agreed to merge under the 80-year-old Ishihara's leadership, despite serious policy gaps, such as the role of nuclear power in Japan's energy mix.

Analysts see the election ushering in a period of confusing coalition politics, partly because of a spate of new parties courting voters discontented with the LDP and the DPJ and because whoever wins will still lack a majority in parliament's upper house, which can block bills.

Prime Minister Yoshihiko Noda dissolved the lower house of parliament on Friday, but the election is unlikely to fix a policy stalemate that has plagued a country struggling to cope with an ageing population, a declining manufacturing sector and the emerging power of China.

Polls by other news outlets, the Asahi Shimbun daily, the Mainichi Shimbun daily and Kyodo, produced a similar LDP lead. But they also showed large numbers of undecided voters -- 44 percent of respondents in the Asahi, 43 percent in the Kyodo and 36 percent in the Mainichi -- who said they did not support any particular party, a sign of campaign battles to come to win over swing voters.

Asked which of the two main parties' leaders was suited for the prime minister's post, 35 percent of those polled by Kyodo chose LDP chief Shinzo Abe, a former premier who advocates aggressive monetary easing, compared with 32.1 percent for Noda.

The DPJ swept to power in 2009 ending more than a half a century of nearly non-stop Liberal Democratic Party rule.

But the support rate slumped over what voters saw as broken promises, a confused response to last year's tsunami and nuclear crisis and Noda's embrace of unpopular causes such as rise in the sales tax and the restart of nuclear reactors.

Following is a table based on media polls asking which party voters would choose in the proportional representation stage of the lower house election.

POLL DATE DPJ LDP RESTORATION

Kyodo Nov 19 10.8 23.0 6.8

Nikkei Nov 19 16 25 11

Asahi Nov 19 15 22 6

Mainichi Nov 19 12 17 13

Yomiuri Nov 18 13 26 8

Asahi Nov 17 16 23 4

Asahi Nov 13 12 29 5

Yomiuri Nov 5 10 25 12

Kyodo Nov 4 12.1 27.7 10.8

Nikkei Oct 29 11 27 13

Asahi Oct 22 13 36 3

Kyodo Oct 3 12.3 31.3 13.9

Yomiuri Oct 3 18 36 13

Asahi Oct 3 17 30 4

Nikkei Sept 28 14 35 12

Asahi Sept 11 15 23 5

Kyodo Sept 2 12.4 22.2 17.6

Yomiuri Aug 13 11 21 16

Mainichi Aug 13 14 21 N.A.

Kyodo Aug 12 14.3 23.5 10.7

Asahi Aug 6 13 23 N.A.

Yomiuri July 16 14 18 N.A.

Kyodo July 15 14.1 19.2 13.2

Asahi July 10 14 22 N.A.

(Reporting by Kaori Kaneko and Kiyoshi Takenaka; Editing by Ron Popeski)