(Adds chief cabinet secretary comment)
By Linda Sieg
TOKYO, Jan 14 (Reuters) - Two former Japanese prime ministers challenged incumbent Shinzo Abe's pro-nuclear power policy on Tuesday, with charismatic Junichiro Koizumi backing ex-premier Morihiro Hosokawa's bid to become Tokyo governor on a platform opposing atomic energy.
Hosokawa's candidacy could turn the local election into a referendum on Abe's energy policies and boost the anti-nuclear movement, which has lost momentum after a surge following the March 2011 Fukushima disaster, the world's worst nuclear accident in 25 years.
Surveys show most voters favour abandoning nuclear power, but the electorate nonetheless propelled Abe's pro-nuclear Liberal Democratic Party (LDP) back to power in December 2012, largely because of his promises to revive the economy and divisions among anti-nuclear opposition forces.
Asked why he was coming out of retirement to seek the Tokyo governor post, Hosokawa, 76, told reporters: "Because I have a sense of crisis that Japan faces various problems, especially nuclear power that could imperil the fate of the country."
Koizumi, one of Japan's most popular prime ministers from 2001 to 2006, has already nagged Abe with his anti-nuclear power pitch, a turnabout from the days when led the LDP.
"The biggest reason why I support Mr. Hosokawa is his view that Japan can prosper without nuclear power," a silver-haired Koizumi, 72, told reporters.
Hosokawa, heir to a samurai lineage, seized the imagination of a public weary of decades of scandal-tainted LDP rule when he formed the pro-reform Japan New Party in 1992. The next year, he took power at the head of a multi-party coalition that ousted the LDP for the first time in nearly 40 years.
But his unwieldy coalition fractured and Hosokawa stepped down after just eight months amid a financial scandal. He was never charged but his image as a bold reformer was tarnished, and he retired from politics in 1998, taking up pottery instead.
How much of a threat the Hosokawa-Koizumi duo poses to Abe is hard to gauge, but Koizumi could be a draw on the campaign trail, while the candidacy could tap into a deep well of anti-atomic power sentiment even as the government seeks to restart nuclear reactors off-line since the Fukushima disaster.
A tsunami crashed into the plant on March 11, 2011, causing fuel-rod meltdowns, radioactive contamination of air, sea and food and triggering the evacuation of 160,000 people in the world's worst nuclear accident since Chernobyl in 1986.
"Given that the LDP government has been seeking to resume nuclear power generation slowly and quietly without drawing too much popular attention, Hosokawa's candidacy is bad news in itself," said Sophia University professor Koichi Nakano.
"What Hosokawa and Koizumi show is that the anti-nuclear hopes are not held just by left-wing radicals, but also by a good number of middle class including even those who are conservative otherwise."
A survey by the local Tokyo newspaper showed that about two-thirds of Tokyo voters want to exit nuclear power sooner or later, while just over nine percent back the government policy.
A government panel said last month that Japan should embrace nuclear power as an "important and fundamental" energy source, rejecting the previous government's plan to abandon atomic energy after the meltdowns at Tokyo Electric Power Co's Fukushima Daiichi plant.
Still, Hosokawa's age and the way he left office could cloud the outlook for his campaign.
"Hosokawa has little direct contact with Tokyo and Tokyo governor elections are more about name recognition and local connections than policies," said Jeffrey Kingston, director of Asian Studies at Temple University's Japan Campus.
The Tokyo poll follows the resignation in December of then-governor Naoki Inose - three months after he helped the capital win its bid for the 2020 Olympics - over his receipt of 50 million yen ($484,000) from a scandal-hit hospital chain.
"Twenty years ago, Mr. Hosokawa stepped down as prime minister due to a problem regarding money - twice as much money as in Mr. Inose's case - from Sagawa Kyubin," Chief Cabinet Secretary Yoshihide Suga told reporters.
"I wonder how this will be viewed by people in Tokyo."
Hosokawa resigned in 1994 amid criticism over a 100 million yen loan he had taken 12 years earlier from the scandal-tainted Sagawa Kyubin trucking firm.
Other candidates include former air force chief of staff Toshio Tamogami, who resigned in 2008 after denying in an essay that Japan was the aggressor in World War Two. He heads the nationalist group "Gambare Nippon" (Stand Firm! Japan). ($1 = 103 yen) (Additional reporting by Tetsushi Kajimoto and Kiyoshi Takenaka; Editing by Nick Macfie)