The main opposition Democratic Party on Saturday urged the government to withdraw its plan to send an inspection team to Japan to assess Tokyo's plan to discharge radioactive water from the crippled Fukushima nuclear power plant, saying it would only "give justification" to Japan's plan.

Rep. Park Sung-joon, the Democratic Party's spokesperson, said the Japanese government has no plan to allow the Seoul delegation to inspect the safety of the release and will go ahead with the plan in July regardless of the team's activities.

"The Japanese government's attitude makes it clear that the inspection team the government is sending is only a formality to justify its plan to discharge contaminated water," Park said in a written statement.

Earlier in the day, Seoul's foreign ministry said South Korea and Japan have agreed that the delegation will visit Japan for four days. It came days after President Yoon Suk Yeol and Japanese Prime Minister Fumio Kishida agreed Sunday on the dispatch of experts from Seoul.

According to Park Ku-yeon, the first deputy chief of the Office for Government Policy Coordination, the inspection team will comprise some 20 experts in safety regulation, check the operation of treatment and discharge facilities in Fukushima and secure the information South Korea needs to conduct a scientific evaluation of the contaminated water. It reportedly plans to visit Japan starting May 23.

But earlier this week, Japanese Industry Minister Yasutoshi Nishimura said the inspection is intended to "help deepen understanding" about the safety of the release, not to evaluate or certify its safety.

"An inspection team that would only review information provided by the Japanese government and take a look around areas the Japanese government allows access to cannot evaluate safety properly," the Democratic Party spokesperson said.

He called on Yoon not to send the team and conduct a separate and more thorough assessment of Japan's plan instead.

The inspection comes amid concerns over possible health and environmental hazards from the release of more than 1 million tons of water from the wrecked plant.

The Fukushima plant has stored more than 1.3 million tons of water through a custom purification system known as the Advanced Liquid Processing System since three reactors melted down after a powerful earthquake struck off the coast in March 2011.