Former motorcycle world champion Wayne Gardner has described his stint in a Japanese prison as the worst 12 days of his life.

The 57-year-old was jailed this month after being accused of assaulting three men during an alleged road rage incident in the town of Motegi, where his son, Remy, was racing.

He arrived in Sydney this morning and said he had been kept isolated from the outside world, receiving “not much” help from the Australian government.

Gardner was accused of road rage. Photo: ABC

“It was horrendous, I never want to do that again. I haven’t been able to have contact with anybody, that’s the problem,” he said.

“Been locked up in a cell for 12 days and no communication with the world, it was pretty horrific.”

“It was horrendous, how they treat you in the communications, and I’m just horrified by it all.”

Asked if he was going back to Japan any time soon he laughed and said “no, not immediately no”.

“I just want to see my parents and make sure they’re OK. It’s the first time I’ve been to jail, so it’s a bit of a shock to everybody,” he said.

As Gardner and his son Remy were arriving at the Motegi Twin Ring racetrack for a race last week, they were involved in a minor collision with another car.

Gardner was held in a police cell in the town of Shimotsuke, about 120 kilometres north of Tokyo, where he was reportedly questioned almost every day by police about the incident.