Sir Jackie Stewart has claimed world motorsport bosses are biased towards Ferrari in the McLaren 'spygate' row.
McLaren believe they will be "completely exonerated"
McLaren go before the World Motor Sport Council in Paris on Thursday amid claims that new evidence could lead to Ron Dennis's team being punished.
But Stewart accused F1's governing body of mounting a "witch-hunt" against Dennis which would backfire on them.
"It seems some of the most powerful people (in F1) are more aligned to Ferrari than anybody else," he said.
"The FIA have historically been very close to Ferrari, closer to them than anyone else.
"There are more Ferrari representatives on the World Council than anybody else."
There's been a transfer of information going on since 1950, when modern Formula One began
Ferrari have accused McLaren of benefiting from a 780-page dossier of information sent by former performance director Nigel Stepney to McLaren's now-suspended chief designer Mike Coughlan.
Three-time world champion Stewart added: "I'm not saying that there hasn't been wrongdoing.
"But to start witch-hunting and trying to implicate a team principal (Dennis) to a level that is currently going on, I think is negative to the sport."
An FIA spokesperson rejected Stewart's accusations, stating: "The suggestion that the FIA's ongoing investigation is about anything other than the pursuit of sporting fairness demonstrates a blinding refusal to accept the basic facts."
Williams F1 team principal Sir Frank Williams echoed Stewart's fears, however, saying: "This may cost Formula One some business.
"I just have concern that if it goes on much longer, it will deter sponsors who are currently in F1, or who are close to coming in."
Even Ferrari boss Jean Todt conceded: "We are sorry it is happening in our sport, but we are in the position where we want the truth to appear.
"That's all that we want, and we are confident the truth will come through."
McLaren were found guilty at a first hearing in July of "fraudulent conduct", but the WMSC said there was insufficient evidence that the team had used the Ferrari dossier to their advantage.
Stepney, sacked by Ferrari, has denied supplying the confidential information to Coughlan. McLaren said at last weekend's Italian GP that they were confident of being "completely exonerated" on Thursday.