The comments made on Monday are already raising anger in neighbouring countries that bore the brunt of Japan’s wartime aggression, and that have long complained that Japan has failed to make amends for wartime atrocities.

Toru Hashimoto, the young, brash mayor of Osaka who is also co-leader of an emerging conservative political party, also told reporters that there was not clear evidence that the Japanese military coerced women to become what are euphemistically called “comfort women”.

“To maintain discipline in the military, it must have been necessary at that time,” said Hashimoto. “For soldiers who risked their lives in circumstances where bullets are flying around like rain and wind, if you want them to get some rest, a comfort women system was necessary. That’s clear to anyone.”

Historians say up to 200,000 women, mainly from the Korean Peninsula and China, were forced to provide sex for Japanese soldiers in military brothels.

More: Japan Mayor Says Wartime Sex Slaves Necessary