Swimming Australia on Friday sacked a member of its Olympic coaching staff, saying he caused serious reputational damage by supporting a rival South Korean athlete racing against his countrymen.

Coach Michael Palfrey caused a stir when he said he hoped Kim Woo-min -- who he coached at one point -- would win the men's 400m freestyle instead of two Australians.

Head coach Rohan Taylor said Palfrey's actions were "un-Australian", but the team did not sack him at the time because it would be too disruptive.

"Swimming Australia has terminated Michael Palfrey's employment due to a breach of his employment agreement," governing body Swimming Australia said Friday.

"Palfrey was found to have breached his employment contract by bringing himself into disrepute and causing serious damage to his and Swimming Australia's reputation, and adversely affecting Swimming Australia's interests."

Palfrey worked with Australian swimmers Zac Incerti, Abbey Connor and Alex Perkins.

But he also mentored South Korea's Kim while he was training in Brisbane ahead of the Games.

Palfrey was wearing Australian team colours when he was interviewed by South Korean journalists and asked about Kim.

"I really hope he can win, but ultimately I really hope he swims well," Palfrey said.