Formula One was last night preparing for a storm of protest after Flavio Briatore, Renault’s team principal, walked out of a court knowing his team had escaped punishment even though they were found guilty of spying. The FIA, Formula One’s governing body, put Renault in the dock at a specially convened hearing in Monaco to answer charges that they were in possession of secret documents belonging to their rivals at McLaren.

McLaren were fined a record $100 million (about £49 million) this year after being found guilty of possessing secrets belonging to Ferrari in an almost identical case. But this time there was no such draconian punishment in a judgment that will astonish many in Formula One and almost certainly trigger a new bout of accusations that McLaren are the victims of the FIA’s legal process.

FIA officials were last night working on an explanation of the judgment and promised a full transcript of proceedings will be published later today in the interests of transparency. The explanation will need to be convincing for millions of Formula One fans who will be unable to equate the severity of the punishment handed out to McLaren with the almost polite rap on the knuckles for a Renault team who appear on the face of it to have committed a similar offence.

Fans will also be entitled to ask why Bernie Ecclestone, Formula One’s promoter, and Jean Todt, the Ferrari team principal, were entitled to vote on the case as members of the FIA World Motorsport Council, given their interests in the case. Todt was the prime mover in bringing McLaren to book when it was discovered that Nigel Stepney, Ferrari’s former chief mechanic, had peddled a 780-page dossier containing secrets about the team’s cars and working methods to Mike Coughlan, McLaren’s chief designer. McLaren, at a first hearing on July 26, were also found guilty without penalty but subsequently hit with their huge fine and erased from the 2007 World Championship, handing the constructors’ title to Ferrari.

Ecclestone is a close friend of Briatore and also his business partner as co-owner of Queens Park Rangers, the struggling Coca-Cola Championship football team. The pair are also known to work closely in the Formula One paddock, where Briatore has Ecclestone’s ear on big decisions. As he left the FIA hearing last night, Ecclestone was asked if the judgment was fair. He said: “Was it fair? We are always fair.”

A glum Martin Whitmarsh, McLaren’s chief executive, was circumspect, refusing to condemn the decision. But his team have fallen at every legal hurdle this year and face a new inquiry today when the FIA will rule whether the car they have built for Lewis Hamilton’s assault on the 2008 World Championship is legal. FIA investigators have mounted a forensic examination of the car to discover whether there any traces of influence from designs contained in the Ferrari dossier. If there are, the McLaren car could be ruled illegal, a massive setback for Hamilton’s chances next season and probably the end of McLaren as title contenders.

Max Mosley, the FIA president, refused to go into detail on the decision-making process last night but will have to be at his best today as he explains how Renault, who admitted that nine engineers had seen secret McLaren information on computer disks, could escape any form of punishment. It is also understood that the team - unlike McLaren from their first July hearing - will not be subject to further examination unless there is compelling evidence for a new investigation. Mosley said: “The full decision when it is published will explain everything.”

The FIA World Motorsport Council started the day knowing that justice not only had to be done in the Renault case, but had to be seen to be done. That could mean that the facts in this case are very different from those that condemned McLaren to one of the most draconian sentences in the history of any sport, let alone Formula One. The facts will only become known on publication of the transcripts of the hearing, but Mosley will mount a stern defence of the FIA and emphasise the organisation’s impartiality in the face of criticism that there appears one rule for Formula One and another for McLaren.

Outside observers unable to make the fine legal distinctions between the McLaren case and that of Renault, who admitted that they possessed McLaren’s secret information and that it had been seen by key members of their team, may struggle to see the differences that let Renault off the hook.

The suspicion will remain that Renault had power to wield as one of Formula One’s top four teams and as a key component in the running of the Formula One show. Carlos Ghosn, Renault’s chief executive, is known to be lukewarm about his company’s involvement in Formula One and an embarrassingly tough punishment may have convinced him to withdraw, causing problems for the Formula One circus. The company also supplies engines for the GP2 feeder series and the Red Bull Formula One team.

The FIA has been under sustained attack in recent times, as the McLaren case unfolded, from leading motorsport figures, such as Sir Jackie Stewart, the three times Formula One world champion, and Damon Hill, the 1996 champion and president of the British Racing Drivers’ Club. Last night’s decision is unlikely to convince them that justice has been seen to be done. That is now for Mosley to explain today.