Former professional racing car driver who raped a 6-year-old girl free after just 6 months jail.

The son of racing legend Sir Jack Brabham, who was found guilty of the rape of a six-year-old girl, has walked free after serving just six months jail.

Less time than many car thieves serve.

Gary Thomas Brabham, 54, was found guilty in Brisbane in March of one count of rape and one count of the indecent treatment of the girl, now aged 19, between 2003 and 2007.

The first incident happened while the girl, who was five or six at the time, was sitting on the racing car driver's lap as he drove a car down to drop off the wheelie bins at a property on Brisbane's west side.

The girl's mother took her daughter to police after she told her of the abuse in October 2013.

During his trial the court was read a letter written by the girl to her mother where she said Brabham “had been touching me repeatedly for many years” and he “had touched her vagina and touched her sexually ... multiple times”.

He was sentenced to 18 months prison in April but suspended after six months and now, Seven News reports the child molester has walked free.

A petition over his "lenient sentence" has been signed by more than 115,000 people.

The petition, set up three days ago, calls on Queensland Attorney General Yvette D'ath and Queensland Premier Annastacia Palaszczuk to reconsider an urgent review into the sentence.

It reads: “I’m friends with the victim’s mum. The judge reported that Gary showed "no remorse". He even tried to appeal this lenient sentence. He's now out, free to abuse innocent victims again.”

“He’s the son of a famous racing driver, using his family’s wealth to throw cash at lawyers to fight his way through the justice system.”

“Yet the Queensland justice system is allowing this behaviour, continuing to fail abused children, knowingly letting a child sex offender walk our streets.

It's time to put an end to these dangerously lenient sentences for child sex abusers in Queensland - please sign and share my petition to the Premier!”

The Courier Mail reports that Brabham had his name suppressed as he served out his time and his family kept the details closely under wraps.

On his release, when he went to revive his career Brabham claimed to have been overseas. It was only when he was convicted a second time that the details became public.

It was Brabham's father, Sir Jack, who was the real motor racing star. He was a three-time Formula One champion, he died on the Gold Coast in 2014 at 88.

Gary Brabham made a foray into Formula One in 1990 and had two starts in the Indy Car World Series in 1993 and 1994 before retiring in 1995.