Shane Rose, a three-time Olympic medallist show jumper, has been stood down by authorities for wearing a mankini on horseback in a fancy dress competition.

Equestrian Australia, his national governing body, said it was obliged to investigate his attire at the show jumping meet near Sydney after “concerns were raised”.

Rose, who won team eventing silver at the 2008 and 2020 Olympics and bronze in 2016, wore three costumes, a fluorescent orange mankini, a gorilla costume and a Simpsons cartoon outfit.

The Paris 2024 hopeful had sparked complaints after posting footage on Facebook of himself in the Borat-inspired swimsuit at the Wallaby Hill Extravaganza in the NSW Southern Highland.

“If my costume offended anyone, I am truly sorry as this was never my intention,” the 50-year-old has now written to his followers after deleting the video.

Equestrian Australia denied claims it was overreacting, saying it “has an obligation to address these concerns and is currently reviewing the matter”.

Rose said he deleted his social media apology to de-escalate the issue and told the Sydney Morning Herald he wanted the situation resolved quickly.

“With a bit of luck this will all be a bit of a laugh in a few days and we can all move on,” he said. “I wore a costume which you could see at a theme park or a beach. Potentially no one has done it on [a] horse, but there you go. I think I am a good person and I do a lot for the sport, and for people in different situations. I don’t feel like I have done anything particularly bad. In hindsight, I should have re-thought what I did, but at the time I thought it was just a bit of fun.”

Darren Gocher, Equestrian Australia chief executive, said children were at the event. “Whether it is one [complaint] or 1,000, we have an obligation to review it,” he said.

The governing body added: “To be clear, Shane has not been suspended or sanctioned. As is usual in these circumstances for all high performance athletes, he has been stood down from competition for several days while the review is carried out.

“This does not affect his ability to train or otherwise participate in the sport. Equestrian Australia has also encouraged Shane to provide an account of the events if he wishes to do so.”

A petition on Change.org objecting to the decision to stand Rose down has already gained almost 10,000 signatures. “Shane Rose has dedicated his life to equestrian sport and the equestrian community,” the petition reads.