Prime Minister Shinzo Abe rejected a call by the opposition Thursday to open an investigation into his Liberal Democratic Party over its possible role in a land deal for a private, nationalist school in Osaka at the center of growing controversy involving him and his wife.

Abe, who is also LDP president, told a diet session that the most the government can do is cooperate "thoroughly" with the Board of Audit, which is independent of the Cabinet, in the fact-finding efforts.

Abe's testimony came on the same day a new video emerged of his wife, Akie, speaking to the school in April 2014, asking the students if they knew who her husband was and hearing them say he was the man who protected Japan from China.