Japan's former prime minister Yukio Hatoyama (R) joins an anti-nuclear demonstration outside his old office in Tokyo July 20, 2012. In a rare move by a former Japanese leader, Hatoyama took part in the demonstration, a fresh sign that the ruling party he once led is fracturing over energy and other policies. REUTERS/Mari Saito

Tokyo - An ex-prime minister joined a weekly mass rally outside his former official residence Friday to protest against the restart of nuclear power generation in post-disaster Japan.

“I regret that politics has strayed far from the people's wishes,” Yukio Hatoyama, who served as Japan's premier for nine months to June 2010, told protesters outside Prime Minister Yoshihiko Noda's official residence.

“We must protect the new trend of democracy you represent. We must stop the restart of nuclear power plants,” the 65-year-old politician, who belongs to Noda's ruling Democratic Party of Japan (DPJ), said.

Hatoyama, who is seen as a maverick by some, and an opportunist by others, later walked to the premier's residence in central Tokyo.

He asked Noda's chief cabinet secretary, Osamu Fujimura, to tell the premier to heed the people's will against nuclear power generation, according to media reports.

Jiji Press news agency estimated the rally, which has been held every Friday since late March, to be around 7000.

Anti-nuclear demonstrations have grown in size since Noda gave the green light on June 16 to restart two reactors at the Oi plant in western Japan.

The decision was taken despite a lack of public trust in safety measures after a massive earthquake and tsunami sparked meltdowns at the Fukushima Daiichi plant in March last year.

One of the two reactors at Oi resumed full operations on July 9 and the other was back online this week.

A separate anti-nuclear rally was held at a park last Monday, a public holiday, with turnout estimated by the organisers at 170 000. Police told media 75 000 had gathered.

Japan was left without nuclear power for about two months since early May when the last of its 50 working reactors was shut down for regular safety checks.

The government took the decision to restart the two Oi reactors as they seek to head off a summer power crunch and are considering lifting the freeze on other units.

Hatoyama was the first DPJ premier after his centre-left party swept to power in a 2009 electoral landslide, ending half a century of conservative rule.

He stepped down in 2010 and his two successors, Naoto Kan and Noda, are said to have gradually reneged on the party's people-first policies.

In the lower house last month, Hatoyama voted against Noda's unpopular bill to double the country's sales tax to 10 percent. The bill is pending in the upper house after its passage through the lower house. - Sapa-AFP