A U.N. watchdog issued a fresh call Friday to Japan to take full blame for forcing women from Korea and elsewhere in Asia to work as sex slaves during World War II.

The U.N. Committee on the Elimination of Racial Discrimination said that by failing to treat the ageing survivors properly, Japan had let their suffering drag on for decades.

"What we're asking the Japanese government is to conclude investigations into the violations of the rights of comfort women by the military and to bring to justice those responsible and to pursue a comprehensive and lasting resolution to these issues," said Anastasia Crickley, deputy head of the committee.

"We're asking them to provide apologies and provision of adequate reparation to surviving comfort women and their families," Crickley told reporters.

"We also believe it’s very important that denial of these events is not countenanced," she added, noting that Japan also lacked legislation banning racist hate speech.

The U.N. panel, made up of 18 independent human rights experts, earlier this month reviewed Japan's respect for an international anti-racism accord.

All U.N. members that have signed the accord are assessed at regular intervals.

U.N. human rights Chief Navi Pillay, who retires on Monday, has repeatedly called Tokyo out over wartime sexual slavery.

Last month the U.N. Human Rights Committee, which monitors compliance with a treaty on civil rights, also pressed Japan on the issue.

Around 200,000 women, mainly from Korea but also China, Taiwan, Indonesia and other Asian countries, were forced to work in Japanese military brothels as "comfort women".

The victims have failed to obtain redress for their treatment despite repeated efforts since the war, and their numbers are dwindling as the years pass.

Japanese courts have thrown out claims for reparation and rejected calls for criminal probes, citing the passing of the statute of limitations.

The country's schoolbooks are frequently criticized for failing to tackle the issue frankly.

Japan issued a landmark apology in 1993 and mainstream public opinion holds that the wartime militarist government was culpable.

"We note the efforts that have been made by the Japanese state to resolve the issue of foreign comfort women who were exploited by the Japanese military," said Crickley.

"We also note the information that we have received from the Japanese state with regard to compensation," she added.

Japan set up a state-fund compensation program in 1994 which made several hundred payouts before it was wound up in 2007.

But a slice of the political right, including current Prime Minister Shinzo Abe, continue to cast doubt on the women's ordeal, claiming the brothels were staffed by professional prostitutes.

Japan earlier this year undertook a review of the issue which upheld the apology but asserted there was no evidence to corroborate the women's testimony, sparking regional anger.

"We are bearing in mind the human rights violations against surviving comfort women. As long as these persist, their rights to justice and reparation are not fully realized," said Crickley. (AFP)