LONDON (Reuters) - Formula One's governing body is facing a major challenge from commercial interests seeking total control of the sport, International Automobile Federation (FIA) President Max Mosley has warned.

The 68-year-old Briton, who is fighting to keep his job after a sex scandal, suggested in a letter seen by Reuters that the media were also being manipulated by those same interests to 'undermine' his position.

"During my period as FIA President the economics of Formula One have changed beyond all recognition," Mosley wrote to presidents of FIA member clubs to explain why he needed to remain in office until the end of his term in October 2009.

"We are now dealing with a sport involving billions of dollars and interests that would like nothing better than to remove the FIA from the championship entirely.

"I have been determined to fight for the rights and role of the FIA in Formula One and it is possibly for this reason that the media have been encouraged by those who have an interest in undermining my presidency."

Mosley has faced numerous calls to resign since the British Sunday tabloid published details and photographs in March of him taking part in what it said was a Nazi-style sado-masochistic orgy with five prostitutes.

The motor racing head, whose father Oswald founded the pre-World War Two British Union of Fascists, has denied any Nazi connotations and is suing the paper for unlimited damages for breach of privacy.

CORE ELEMENTS

In his letter sent on Friday, Mosley said it would be "irresponsible, even a breach of duty, to walk away from a number of negotiations currently under way, all of which are of fundamental importance to the FIA."

He said the FIA was in the middle of a renegotiation of the 100 year agreement with the commercial rights holder (CRH), represented by Bernie Ecclestone, that effectively governs Formula One.

In 2001, the FIA sold Ecclestone's family holding company SLEC a 100 year extension to their commercial rights from 2010 in a $309 million (158 million pound) deal. CVC took control of the commercial rights in 2005, with Ecclestone still at the helm.

"The CRH originally asked us to accept changes to the agreement in order to reduce the CRH's liability to tax," said Mosley.

"These we can probably concede. But the CRH has also now asked for control over the Formula One regulations and the right to sell the business to anyone -- in effect to take over Formula One completely. I do not believe the FIA should agree to this.

"To do so would be to abandon core elements of the FIA's patrimony including, for example, our ability to protect the traditional grands prix.

"We would also be weaker financially but, even more importantly, we would put at risk the viability of the FIA as the regulatory authority of international motor sport..." Mosley added.

The FIA president said the rights holder and teams also wanted a new Concorde Agreement, governing the commercial side of the sport, as another way of exercising control.

"The sport and the commercial interests should be kept separate," he said. "The teams and the CRH should be consulted and listened to at all stages but it must be the FIA, not the CRH or the teams, which decides the regulations.

"My refusal to concede on this has led to a difficult situation and compounds the problem with the CRH over the 100 year agreement."

(Reporting by Alan Baldwin, editing by Clare Lovell)