TOKYO, June 5 (Reuters) - Nearly a third of Japan's ruling party lawmakers are petitioning Prime Minister Yoshihiko Noda to be cautious about restarting nuclear reactors given safety concerns after last year's earthquake and tsunami, an organiser said on Tuesday.
Noda, keen to restart two reactors in western Japan before electricity demand peaks this summer, could decide as early as this week to reconnect them to the grid - despite the risk of a backlash that would weaken his already sagging voter ratings.
"It is clear from surveys that the majority of the people think that we can survive this summer by conserving energy and transferring electricity among regions," said the petition, to be presented to Noda's government later in the day.
"We urge you to consider the fact that there is insufficient agreement within the party and among the people and the feelings of the 160,000 victims of the disaster, and be all the more cautious about a decision to restart the reactors."
Nuclear power supplied nearly 30 percent of Japan's electricity needs before last year's earthquake and tsunami crippled the Fukushima plant in northeast Japan. But all of the country's 50 reactors have since been taken offline for checks.
Noda on Monday stressed that restarting the idled reactors was vital not just to survive summer power shortages but also to avoid hurting the economy with higher electricity rates, a view commonly voiced by Japan's struggling manufacturers.
But Satoshi Arai, an ex-national strategy minister sponsoring the petition, said Noda had failed to meet conditions for resuming operations at the two Kansai Electric Power Co reactors at its Ohi plant in Fukui, western Japan.
The government has been struggling to win support from local authorities for the restarts, but on Monday the governor of Fukui said the ball was in Noda's court. (Reporting by Linda Sieg; Editing by Nick Macfie)