SEOUL (REUTERS) - More Olympic athletes are set to ditch their South Korean passports and compete for rival nations unless the country's skating union (KSU) reforms, the father of Korea's greatest sporting defector has told Reuters.

Anger with the KSU has boiled among Koreans following Ahn Hyun Soo's cross-over to Russia in 2011 - and was only exacerbated when the 28-year-old won his fourth, fifth and sixth Olympic gold medals in Sochi under the name Viktor Ahn, and as a Russian competitor.

It was a painful episode for a proud country. Ahn had won his first three golds as a South Korean at the Turin Olympics in 2006, but then came quarrels and clashes, failure to qualify for the 2010 Games and the decision to quit Korea and become a Russian citizen.

It was a huge step, but one others may soon take, his father told Reuters, claiming that more are ready to follow his son out the door and into the arms of other nations unless the Seoul-based skating union sorts itself out.

"I assure you, and I am saying this with confidence, there are some parents whose children won medals at the Olympics and who have told me if the KSU keeps going like this, they are also considering switching nationalities," Ahn Ki Won told Reuters.

Speaking at his local rink he said he would not allow his youngest son, Hyun Jun, another promising young short track speed skater with Olympic ambitions, to go through the same torment as his older brother, who he still refers to as "Hyun Soo" rather than "Viktor".

"If the KSU refuses to reform and goes on the way it has, I'm considering switching my youngest son's nationality to give him a better opportunity.

"I'm not doing all this for Hyun Soo, I'm doing this for Hyun Jun. I'm doing this for the next generation of South Korean skaters."

Ahn Ki Won, who has been highly critical of the KSU for a number of years, told Reuters his son had been shunned, bullied and beaten in the Korean team, and that the poisonous atmosphere had eventually driven him to turn his back on his homeland.

The skater's trio of golds in Sochi in February sparked a furious backlash in South Korea. Irate fans vented their fury at the KSU, and the nation's President Park Geun Hye demanded to know how the country could let one of the greatest Olympians of all time slip through its fingers.

His father said factional divisions and power struggles within the KSU were tearing the heart out of the Korean short track team, where bias and favouritism had led to athletes turning on one another.

"Watching him win the gold medals in Sochi, I won't say it was a feeling of revenge... but it was something cathartic...

"All I want is this: to make the KSU transparent, democratic and to keep those with power in check," he said.

KSU vice-chairman Jeon Myung Gyu resigned on Monday, though the reason given for his departure was the poor performance of the men's team in Sochi, not the circumstances that prompted Ahn's switch to Russia.

Ahn Hyun Jun is just 13, but is already having to live with comparisons to his older sibling. He said he missed his big brother but was happy he was enjoying life in Russia.

"I haven't got to a level yet where I'm good enough to even think about changing nationality, but it's not out of the question," he said, adding that he wanted to skate for the Korean team on home ice at the 2018 Pyeongchang Winter Games.

"Even if we meet as competitors, with him representing Russia and me competing for Korea, I think that's OK. I'll enjoy the competition."

His father is keeping a close eye on his development, determined to protect him from any mistreatment if and when he makes it onto the Korean team.

He watches with pride as his youngest son zips around the rink, hands behind his back, gliding effortlessly behind the leader in a train of young short track skaters.

"He skates just like his brother," he tells Reuters with a broad smile.

Good news for Korea. Or Russia, perhaps.