Former Ferrari team principal Jean Todt of France and ex-world rally champion Ari Vatanen of Finland will face off for the presidency in an Oct. 23 vote.
"The FIA will be calling on all candidates to avoid negative campaigning and prejudicial leaks to the media," the organization said Friday in a statement. "Candidates should focus on the positive aspects and opportunities of the upcoming election and its effect on motoring and motor sport."
FIA published a letter from Vatanen on its Web site that had previously been leaked to the media. In it, Vatanen threatened Mosley with legal action for what he says is a defamatory statement made against him and a breach of neutrality during the campaign.
"The breach of this principle of neutrality during election campaigns, when aimed at distorting the results of the election, is punishable by all the French courts," Vatanen wrote to Mosley.
Vatanen accused Mosley of showing favoritism toward Todt by regularly expressing his support for the Frenchman's candidacy.
Vatanen, a four-time winner of the Paris-Dakar race, also claimed Mosley wrote to Prince Faisal of Jordan to criticize him.
A big favorite to succeed Mosley, Todt is also backed by Formula One boss Bernie Ecclestone and seven-time world champion Michael Schumacher.
Mosley, who is in his fourth and final term as president, said on FIA's Web site that he was "surprised" by Vatanen's criticism and asked Vatanen to provide any evidence of wrongdoing so FIA could open an investigation.
"If you know of a specific act on behalf of either candidate which you think conflicts with the law, please give me the details together with a precise explanation as to why you think it illegal," Mosley wrote.