"I think I have to apologise firmly for what Japan did as I talk to former comfort women," Toru Hashimoto, who is co-leader of the national Japan Restoration Party, told a television interview.
"I will tell the comfort women that I'm sorry for having had such a system no matter whether it was forcible or not," Hashimoto said. "It was a disgraceful act and should never be repeated."
"Japan was not the only one doing so," he said. "Everybody was doing bad things. I think Japanese people... should offer objections if there is a misunderstanding of facts in the world."
Hashimoto prompted outrage at home and abroad by saying on Monday that soldiers living with the daily threat of death needed some way to let off steam which was provided by the comfort women system.
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Up to 200,000 women from Korea, China, the Philippines and elsewhere were forcibly drafted into brothels catering to the Japanese military in territories occupied by Japan during WWII, according to many mainstream historians.
The position holds that while there may have been coercion, it was carried out by individuals, gangs or businesses, some of which were non-Japanese.
In Washington, two US lawmakers on yesterday condemned his remarks and urged Japan's central government to distance itself clearly from him.
Japan's government has made no direct comment on the remarks, but has said it stands by pronouncements issued by earlier administrations.
In a landmark 1993 statement, the Japanese government offered "sincere apologies" for the "immeasurable pain and suffering" inflicted on comfort women.