Max Mosley has dismissed Ari Vatanen's suggestion that his open support for Jean Todt in the FIA presidential election constitutes a breach of French law.
In a letter published by the FIA, Vatanen criticised Mosley for backing Todt as his successor, and threatened further action.
"Pursuant to French law, the operation of non-profit organisations is governed by general legal principles," Vatanen wrote.
"Among these general principles, applicable to elections, the principle of equality among all candidates is enshrined in the French Constitution and the corollary to this principle of equality is the principle of neutrality which all persons must adopt who due to their position have a particular influence on voters.
"The breach of this principle of neutrality during election campaigns, when aimed at distorting the results of the elections, is punishable by all of the French Courts."
Vatanen believes that Mosley and other influential Todt backers have acted contrary to this law.
"In the current campaign for the election of the President of the Federation Internationale de l'Automobile, the principle of neutrality has been flouted constantly by the FIA, certain paid staff members, and the employees of certain organisations dependent on the FIA which use the funds made available by the FIA, such as the FIA Foundation for example," he wrote.
"However, you were the first to violate the principle of neutrality.
"Indeed, whereas I announced last 11 July that I was running as a candidate for the Presidency of the FIA, you sent an official letter shortly thereafter on 15 July to all of the Members of the FIA in which you state your intention not to stand for re-election and in which you openly express your support for the candidacy of Jean Todt who moreover, had not yet even officially announced that he was running for the office of President."
The former World Rally champion also cites comments made by Mosley in interviews, a letter he wrote to Prince Faisal of Jordan in which he predicts that Vatanen will lose the election, and actions in support of Todt by other senior FIA figures.
"Under these conditions, I suggest that you stop and that you ensure that staff members on the payroll of the FIA and organisations which depend financially on the FIA stop these practices which up until now have constituted a violation of the principle of equality among candidates to the Presidency of the FIA," Vatanen wrote.
"In addition, I further reserve all right to take action on account of the act previously committed against me."
But Mosley has responded by claiming that Vatanen had previously sought his backing and insisting that his support for Todt does not contravene any law or principle.
"I am surprised you seek to criticise me for supporting the other candidate," Mosley wrote. "You joined me for lunch on 3 July 2009 and repeatedly asked me to support you. You will recall I told you then I would support Jean Todt, as I thought him the better candidate.
"This was not a reflection on you, merely recognition that, in my view, Jean has relevant knowledge and experience while you do not.
"I know of no provision of French or any other law which prevents an outgoing office holder offering his personal view on who is most qualified to be his successor. Equally, everyone involved with or interested in the FIA is entitled to a personal view and to express that view.
"The essence of a free and fair election is that the merits of the different candidates are debated. It is not a violation of any legal principle for anyone to think that you are a less qualified candidate than your opponent for the role in question."
In addition to publishing the two letters, the FIA has also urged Todt and Vatanen to take a positive approach to the final week of campaigning ahead of next Friday's election.
"The FIA will be calling on all candidates to avoid negative campaigning and prejudicial leaks to the media," said a statement on the governing body's website.
"Candidates should focus on the positive aspects and opportunities of the upcoming election and its effect on motoring and motor sport."