Prime Minister Yoshihide Suga on Wednesday faced questions from a major opposition party over issues ranging from his rejection of scholars to an advisory body to the government's coronavirus response.

In their first face-off in parliament since Suga took office in mid-September, Yukio Edano, the head of the largest opposition Constitutional Democratic Party of Japan, criticized the prime minister's decision to keep six government critics off the Science Council of Japan as "illegal" and asked him to clearly explain the reasons behind the decision.

Suga, however, declined to give details on why he did not nominate the scholars who have been critical of security and anti-conspiracy legislation enacted under his predecessor Shinzo Abe.

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Suga said he considered the council's nature as a body for which taxpayers' money is used, while adding that there was a bias among its members in terms of age and educational background, among other factors.

He reiterated that he has no plans to reverse the decision and name the six to the council.

The government understands that it does "not necessarily have to name (all) members as recommended," said Suga, who has jurisdiction over the council.

The response by Suga at the Diet drew a sharp reaction from members of the House of Representatives, forcing its chairman to call for silence several times.

Since the controversy over the council emerged, Suga has seen support rates for his Cabinet fall in media polls from over 65 percent at the outset, marking the end of his honeymoon period.

The issue has reminded people of Suga's time as chief Cabinet secretary under Abe's leadership of nearly eight years, when he took control over the country's powerful bureaucrats and purged those who got in his way, according to political experts.

Suga delivered his policy speech at the start of an extraordinary Diet session on Monday, vowing to achieve net zero emissions by 2050, a move welcomed by the United Nations and countries sharing the goal of going carbon-free.

"It is not easy to attain carbon neutrality by 2050," said Suga when asked about his energy policy and Japan's reliance on nuclear power.

He said the government "will not just pursue renewable energy but all options including nuclear power." But he also said Japan intends to lower its reliance to nuclear power.

"We will work on maximizing the introduction of energy conservation and renewable energy, while lowering our dependence on nuclear power generation as much as possible," Suga said.

On the pandemic, Edano said that face mask shortages, the limited number of coronavirus tests and strains on the medical system have caused significant concern among the public.

Suga vowed to provide necessary support, saying, "I will consider assistance so that we can ensure necessary local healthcare."

He also pledged to implement economic support measures "without hesitation."

Asked about foreign policy, Suga mostly repeated what he said in his speech.

He underscored that the Japan-U.S. alliance is the cornerstone of Japan's foreign policy, saying he seeks to deepen the bilateral ties on a wide range of issues, including response to North Korea, regardless of the outcome of the U.S. presidential election next month.