IndyCar have levied a fine of $30,000 on Penske Racing driver Helio Castroneves, following comments on Twitter in which he branded IndyCar president of competition and operations and race director Brian Barnhart a "circus clown".

Castroneves went on to suggest that Barnhart "changes the rule book when is convenient for him, and his own personal interests" and then wrote a column for a Brazil newspaper headlined "IndyCar has a serious problem and it's called Brian Barnhart."

The outburst came after a penalty Castroneves received at the end of the Indy Japan in Motegi, for overtaking under local waved yellow flags.

"IndyCar has fined driver Helio Castroneves $30,000 and placed him on probation for the remainder of the season for actions following the Sept. 18 IZOD IndyCar Series race at Twin Ring Motegi," read the official statement from the series.

"Castroneves was penalized for use of improper, profane or disparaging language in reference to officials for comments he made toward the Race Director via Twitter," it continued. "Because of the public display of his actions, Castroneves will be able to work off the fine by making a series of public appearances on behalf of IndyCar throughout the remainder of the season."

The fine is less than some were expecting, and the option to "work off" the fine also a surprise, but they match the penalties levied against Castroneves' Penske team mate Will Power for his outburst and obscene gestures toward race control following the controversial end of the MoveThatBlock.com Indy 225 race at New Hampshire Motor Speedway.

At the time, it was thought that Power's slightly lower penalty and option to "work off" the fine was in recognition that Power's indiscretion had happened in the heat of the moment following a restart attempt that even Barnhart subsequently conceded had been a mistake. Power was also immediately contrite and apologised for his outburst once he had calmed down.

Castoneves on the other hand made his Twitter comments sometime after the end of the race and his newspaper column came out two days later. He has not apologised for or retracted his comments, even after the penalty announcement today, simply responding that he was "aware of the fine issued by IndyCar for my comments after the race in Japan.

"At this point, I think it's best to just put this situation behind me and move forward," a statement released through Penske Racing continued. "We have a big race this weekend and my focus now is getting back on track and behind the wheel of the #3 Team Penske car as we try to defend our win from last season at Kentucky Speedway.

"It's important for us to end the season on a positive note so we will be doing our best to get back to Victory Lane this weekend and at the finale in Las Vegas," he finished.

Under the terms of the IZOD IndyCar Series rulebook, Castroneves still has the right to contest the penalty as prescribed. A protest or appeal could result in an increase, decrease or no change to the penalty.

In October 2001, Paul Tracy received a $50,000 fine for branding the Champ Cars chief steward a circus clown. Tracy was fined the same amount in July this year after Twitter comments suggesting that IndyCar CEO Randy Bernard had intervened in race control decisions in Toronto in favour of Dario Franchitti.

Also available: full story of Castroneves' complaints against BarnhartPower fined $30,000 over New Hampshire