Japan on Wednesday launched a new independent nuclear regulatory body in response to claims that cosy relationships and an overly powerful industry were responsible for the disaster at Fukushima.

But critics charge the Nuclear Regulation Authority (NRA) is a watchdog without any teeth and say the installation of an insider to head the organisation was a case of business as usual.

Dissenting lawmakers said the appointment of Shunichi Tanaka as the chairman of the NRA was questionable because he previously served in key positions in entities that contributed to Japan's nuclear energy drive.

However Prime Minister Yoshihiko Noda went ahead with the appointment after Tanaka pledged to keep his distance from nuclear power plant operators.

The launch of the new nuclear watchdog comes as ministers have suggested the government had not quite fully approved a plan to phase out nuclear energy in the 2030s despite its announcement at the end of last week.

Whether Japan will adopt the goal of zero-nuclear energy by 2040 "will be decided by" experts appointed by the industry ministry, Chief Cabinet Secretary Osamu Fujimura told reporters.

Industry minister Yukio Edano said the policy "was not included in papers approved in a cabinet meeting but was authorised by the cabinet" on Thursday.

Japan has faced international and domestic criticism in the months since the disaster at Fukushima over the close relationships between nuclear power companies, the regulators who are supposed to police them and the government.

Erstwhile nuclear regulator the Nuclear and Industrial Safety Agency (NISA) was administered by the industry ministry, which also had responsibility for promoting nuclear power.

The existence of two different regulatory bodies -- NISA and Nuclear Safety Commission (NSC), a body administered by the cabinet office -- also proved an obstacle in dealing with the aftermath of reactor meltdowns at Fukushima.

Critics say the two bodies did not share information and did not cooperate on policy.

The NRA takes over the role as safety regulator from both NISA and NSC, and will be in charge of enforcing tougher rules the government has decided to introduce.

The NRA is also tasked with approving restarts of the country's reactors, most of which have been idled for regular checkups, with public opinion seemingly hardening against allowing their restart.

The NRA will hold its first meeting later Wednesday to discuss how to operate the new organisation, a spokeswoman for the organisation said.

The government says the independence of the NRA is guaranteed by giving it a status similar to the country's antimonopoly watchdog, the Japan Fair Trade Commission.

Ahead of a general election expected this autumn, nuclear energy has become a hot button issue in Japan with protests that sometimes attract tens of thousands of people calling for it to be ditched.