Flamboyant former Japanese premier Junichiro Koizumi on Tuesday called on his one-time protege and the nation's current leader to abandon nuclear power as anti-atomic sentiment runs high after the Fukushima disaster.

The 71-year-old has emerged as a high-profile critic of the nuclear power industry he once supported, a move that surprised Shinzo Abe's administration which is pushing to restart Japan's shuttered reactors.

Abe was Koizumi's right-hand man during part of the latter's 2001-2006 tenure as prime minister.

"I cannot read his mind but I hope he would move toward" going nuclear-free, the popular former premier told the Foreign Correspondents' Club of Japan.

"There is no better environment for the prime minister than right now... if Prime Minister Abe decides now (to go nuclear-free), there would be few parliamentarians who would resist that plan while ordinary citizens would lend their support too."

Koizumi added that "we should go to zero now".

"Restarting the reactors will only result in more nuclear waste."

The Fukushima crisis sparked a national debate over nuclear power -- which once supplied one-third of the country's electricity -- as street protests numbering in the tens of thousands demanded an end to atomic energy.

The demonstrations have largely faded with Abe pushing to restart reactors as Japan grapples with soaring bills for imported energy.

But some high-profile figures including Koizumi have kept up a public battle against nuclear.

Amid speculation he may attempt a return to politics, Koizumi also heaped doubt on suggestions that Japan could find a safe way to deal with nuclear waste.

"If you think there is any feasible plan for building a waste disposal site, that's irresponsible and way too optimistic," he said Tuesday.

Koizumi had once argued that nuclear power was cheap and safe. But that changed after a quake-sparked tsunami slammed into the Fukushima plant in March 2011, sending reactors into meltdown and sparking the worst atomic accident in a generation.

Tens of thousands of people were evacuated from around the plant and decommissioning of the site is expected to take decades.