The issue of women forced into sexual slavery for Japanese troops in the second world war has roiled relations between the neighbours – both of them US allies and both threatened by nuclear-armed North Korea – for decades.

The deal on the so-called “comfort women” should not have been struck without the involvement of the victims, Moon told a New Year press conference.

“This issue cannot be resolved through a give-and-take deal between governments struck over the victims’ head,” he said.

“A wrong knot has to be untied. Japan should accept the truth, make a heartfelt apology to victims.”

Doing so would enable the survivors to forgive it for its past wrongs, he added.

The agreement was finalised by former president Park Geun-hye under pressure from Washington in the face of mounting security threats from North Korea.

Under the deal, South Korea promised not to raise the issue again and Japan transferred 1 billion yen (now US$8.9 million) to a foundation dedicated to supporting the victims.

Tokyo has reacted angrily to comments on the issue this week by Seoul.

Yoshihide Suga, the top Japanese government spokesman and the Chief Cabinet Secretary, said on Wednesday: “Japan can never accept it if the South Korean side demands we take further measures despite the agreement that confirmed the final and irreversible solution on the issue.”

Moon had lambasted the agreement on the campaign trail and was elected president in May after Park was impeached and jailed over a massive corruption scandal.

But he said: “The fact that there was an official agreement between Korea and Japan cannot be denied. It is also important to deal with Korea’s relationship with Japan carefully.”