“Only a part of the record of Mr. Yoshida’s testimony has been picked up and reported by several papers,” said Yoshihide Suga, the top government spokesman. “His original concern that his story would develop a life of its own without verification came to be realized. We think it would lead to a result that is against his will if we don’t disclose it.”

Since the Fukushima disaster, the liberal Asahi Shimbun has campaigned against nuclear power in its editorial pages, saying it regretted its earlier support. The conservative Yomiuri Shimbun has been critical of Asahi’s coverage, saying its report on Mr. Yoshida’s testimony “caused serious misunderstandings among the international media.”

The Asahi Shimbun’s coverage of another delicate topic has also come under scrutiny in recent weeks. Last month the newspaper retracted 16 articles, the first published in September 1982, citing a Japanese Imperial Army veteran who said he had rounded up Korean women to serve as sexual slaves during World War II.

While most historians agree that Japan forced thousands of women to work in a network of wartime brothels, some have long questioned the particular evidence given by Seiji Yoshida, a soldier who later became a writer. Shinzo Abe called him a “con man” in a speech in November 2012, shortly before taking office as prime minister. (Japan did not use Mr. Yoshida’s statements in developing the country’s formal apology to the women.)

Mr. Abe, a nationalist who has vowed in the past to end what he calls a masochistic view of Japan’s history, told a radio program on Thursday that he would not comment directly on The Asahi Shimbun. But he said, “I think it is true that, by the false reporting on comfort women, for example, a lot of people have suffered, and Japan was discredited in international society,” the broadcaster NHK reported.

The Asahi Shimbun said that it sent reporters to Jeju Island in South Korea in April and May to try to corroborate Mr. Yoshida’s claims of his personal involvement in rounding up women to serve as sexual slaves, but that after interviewing about 40 people, they were unable to do so. Mr. Yoshida died in 2000 and had declined to help in previous efforts to investigate his claims, the newspaper said.

In February, Mr. Abe ordered an investigation into the government’s apology for the sexual slaves. That effort prompted criticism from China and South Korea, which say Japan has not come to terms with the brutality of its wars against its neighbors. His government has since said it would not revise the apology.