Japan's opposition bloc on Wednesday stepped up its offensive against Prime Minister Fumio Kishida over his government's plan to raise taxes to boost defense spending, arguing the decision was made without sufficient parliamentary debate.

In the first full-fledged debate since the ordinary parliamentary session began Monday, Kishida only repeated his mantra that he will "continue to politely explain" his policies to the public, drawing heckling from opposition lawmakers.

Kenta Izumi (front), head of the main opposition Constitutional Democratic Party of Japan, speaks during a House of Representatives plenary meeting at the parliament on Jan. 25, 2023. (Kyodo)

In December, the Kishida administration decided to almost double its defense spending over the next five years and acquire enemy base strike capabilities to deter attacks, in a major shift in its security policy amid mounting regional military threats.

The government has also voiced its intention to hike corporate, income and tobacco taxes in fiscal 2024 or later to secure roughly 1 trillion yen ($7.7 billion) yearly to strengthen the country's defense capabilities.

The opposition camp has criticized Kishida, president of the ruling Liberal Democratic Party, for having made such significant decisions after last year's extraordinary Diet session, which closed early last month.

In the plenary session of the lower house, Kenta Izumi, head of the main opposition Constitutional Democratic Party of Japan, urged Kishida to dissolve the House of Representatives for a snap election to seek a popular mandate if he wants to push for the tax hike.

Izumi described Kishida's decision as "reckless" while asking the premier whether strike capabilities could be a "preemptive" approach that violates international law.

Kishida, known as a dovish moderate, emphasized Japan will stick to global rules, saying that the capabilities will be used as the "minimum defense steps" to protect the nation from missile attacks by its enemies.

As for costs aimed at bolstering Japan's defense capabilities, Kishida expressed his readiness to "make utmost efforts" to slash other expenditures to reduce the public burden as much as possible, even after the government increases the levies.

Kishida also said he will "appropriately make a judgment" on when to call a snap election. A prime minister has the final say on the dissolution of the lower house under the Constitution.

The current four-year terms for lower house members expire in October 2025 unless Kishida dissolves the chamber.

During the 150-day session through June 21, meanwhile, opposition parties have been keen to take on Kishida over issues such as an extension of the maximum service period for nuclear reactors and child policies, which he has pledged would be a priority.

It remains uncertain how his administration would cover the costs of implementing measures to facilitate child-rearing, sparking concern in Japan that Kishida could carry out a politically unpopular consumption tax hike.

On the macroeconomic front, Kishida promised that the government will work in tandem with the Bank of Japan to realize growth and price stability in combination with expansion of wages that have shown few signs of sharply rising in decades.

Kishida, however, avoided elaborating on his choice of the successor to incumbent BOJ Governor Haruhiko Kuroda, who is scheduled to end his 10-year career on April 8. The central bank chief has pursued aggressive monetary easing to combat deflation.

The administration will appoint the "most appropriate" figure in light of the economic situation, Kishida said, although he did not mention whether he will tap a candidate would likely reverse Kuroda's monetary policy course.

He also declined to comment on whether to revise the decade-old accord between the government and the BOJ, in which the central bank has committed to achieving a 2 percent inflation target "at the earliest possible time."

Kishida has said his administration will submit to parliament its choice for Kuroda's successor next month.

Regarding diplomacy, Kishida said he will consider visiting Ukraine, under invasion by Russia since February 2022, for talks with President Volodymyr Zelenskyy if the right conditions are met.

"Nothing has been decided at this point, but we will consider" whether to visit Ukraine "in consideration of various circumstances," Kishida said, after Toshimitsu Motegi, LDP secretary general, requested him to follow the example of leaders of other countries.

While Kishida has been eager to make a trip to Ukraine as chair of the Group of Seven summit in May in Hiroshima, a Japanese government official said it might be difficult to arrange his visit to the Eastern European state for security reasons.

At the G-7 gathering, Kishida, a lawmaker representing a constituency in the western Japan city, plans to set out his vision of a world without nuclear weapons with fears intensifying that Russia could use an atomic device against Ukraine in the ongoing war.

Hiroshima was devastated by a U.S. atomic bomb in August 1945.