South Korea apologises for mishandling sexual assault claims against former diplomat in New Zealand

South Korea's Foreign Minister has apologised for mishandling allegations of sexual assault by one of its diplomats in 2017, but advocates say it's "gut wrenching" the offer of remorse wasn't directed to the victim.

It comes after Newshub Nation revealed Korea blocked the police investigation into the former Deputy Ambassador to New Zealand. Instead, Hongkon Kim is in the Philippines as Consul General and Korea is refusing to arrange his return.

But Korea has now admitted there were problems from the start. On Monday night (NZ time), Korean Foreign Minister Kang Kyung-wha admitted the investigation into the allegations was mishandled.

Kim is wanted by New Zealand Police on three separate charges of indecent assault in late 2017.

South Korea-based journalist Raphael Rashid says the ministry's apology is unheard of.

"It's very unprecedented that the Ministry of Foreign Affairs comes out apologising like this for its handling of a case."

But although the ministry apologised, it didn't direct it to the complainant or even at New Zealand. Instead, it said sorry to the Korean public for the concern and embarrassment it's caused.

"I think the apology was aimed at the president because he was quite embarrassed," Rashid says.

New Zealand sexual violence advocate Louise Nicholas has been supporting the complainant and says the apology should be for him.

"He's quite distraught over that and I don't blame him at all. There's no apology or anything for him, and that's gut wrenching."

Foreign Minister Winston Peters has publicly called for Kim to return to face the charges. But whether he does is up to police.

"When they've made a decision, we'll all know," Peters says.

Newshub has repeatedly asked police when they'll apply for extradition, and Korea says it will cooperate if they do. But police won't comment for privacy reasons and while the matter is before the courts.