Helio Castroneves has been placed on probation for the remainder of the IndyCar season and fined $30,000 for his comments after the Motegi race.
The Brazilian hit out at chief steward Brian Barnhart following the penalty he was given in the Japanese race for having overtaken under yellow.
"I acknowledge that (Barnhart) has done a lot for the series, but he has definitely lost it," Castroneves wrote in his column in the Metro newspaper.
"It's impossible to accept the decisions of a race director who is inconsistent, who issues different punishment to identical situations and who is condescending with some and harsh with others."
Castroneves had earlier called Barnhart "a circus clown" on his Twitter account.
On Tuesday, INDYCAR announced the Brazilian has been penalised "for use of improper, profane or disparaging language in reference to officials for comments he made toward the Race Director via Twitter."
"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," said INDYCAR in a statement.
Castroneves will be allowed to appeal the penalty.
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