Nippon Professional Baseball commissioner Ryozo Kato, who has come under fire after the league secretly altered its baseball, insisted anew on Monday he has no plans of stepping down in the wake of the scandal.

"Let history be the ultimate judge in evaluating me," Kato was quoted as saying after returning to NPB headquarters for the first time since attending a news conference there on June 14.

Although Kato has promised to give his full cooperation to a third-party panel investigating the cover-up, he remains adamant, with almost quixotic zeal, about holding onto his post.

"I want to help with the return (of baseball) to the Olympics and also improve the quality of international tournaments. I plan to take on these tasks," he said.

The 71-year-old former Japanese ambassador to the United States has said he was never informed of changes made to this year's ball to make it livelier. But the Japanese players union has called on NPB to select a new commissioner.

"Japanese baseball has the best track record in the world, in terms of the exclusion of gangsters and in dealing with drugs," Kato said.

"I am not trying to throw up a smoke screen, so I hope people will sincerely listen to what I have to say."