Japan's pro-nuclear government is to change some top officials at its nuclear regulator, officials said Wednesday, in what critics charge is an attempt to remove opponents to the restarting of the country's reactors.

Prime Minister Shinzo Abe's administration has told lawmakers it wants to switch two out of five commissioners at the Nuclear Regulation Authority (NRA) when their term in office expires, an NRA official said.

"The personnel change is a blatant attempt to prompt resumption of nuclear plants," Hajime Matsukubo, spokesman for anti-nuclear group the Citizen's Nuclear Information Centre, told AFP.

"The new composition of the commissioners will be four members who are nuclear experts and one non-nuclear expert," he added.

The NRA, which was established in the aftermath of the triple meltdown at Fukushima after the March 2011 quake and tsunami, has showed itself as a watchdog with teeth -- far removed from the supine regulators in office when the disaster happened.

However, their rigorous enforcement of safety standards is proving an obstacle to Abe's desired swift restarting of reactors, with commentators noting that it may be autumn at the earliest before Japan goes nuclear again to generate electricity.

One of those the prime minister wants to replace is Kunihiko Shimizu, a seismologist who has been cool on the idea of restarts in earthquake-prone Japan.

He has declared that at least two reactors sit on active faults, a judgement that appears likely to lead to the eventual scrapping of the units at huge cost to their operators and to the government.

Utility officials and some members of Abe's ruling Liberal Democratic Party, which has traditionally been close to the nuclear industry, have reportedly criticised Shimizu for his stance.

Shimizu's term of office at the NRA, along with that of Kenzo Oshima, former under-secretary general of the United Nations, will expire in September and the government will not reappoint them, the NRA official said.

Under the government's plan, their successors will be Satoru Tanaka, a nuclear power engineering expert, and geologist Akira Ishiwatari, he said.

Tanaka has openly supported the idea that nuclear power should be part of Japan's energy mix, while Ishiwatari is seen as holding a more neutral position.

Chief Cabinet Secretary Yoshihide Suga brushed aside scepticism about the personnel change, saying on Tuesday the candidates for new commissioner posts "are the best people, who can assume their duties independently, with view to science, neutrality and fairness".

Critics say the move is the latest example of Abe's tendency to try to circumvent rules that he does not like on his way to accomplishing policy goals.

Other examples include his ongoing effort to reinterpret Japan's anti-war constitution to allow the armed forces to engage in so-called "collective self defence" -- fighting in defence of an ally -- a move unpopular with the public at large.

He also stands accused of stuffing the upper echelons of public broadcaster NHK with right-wing cronies, one of whom subsequently defended Japan's wartime practice of sex slavery.