Lewis Hamilton's prospects of becoming the first driver to finish as Formula One world champion in his rookie season were under threat last night after a leading member of his team was accused of involvement in espionage against Ferrari.

In a day of sensational revelations that rocked the sport, the Surrey home of Mike Coughlan, 48, the McLaren Mercedes chief designer, was searched by police after a tip-off from Ferrari about the alleged theft of a large amount of technical information from their factory in Maranello, Italy.

Ferrari are linking the information allegedly found in Coughlan's possession with their investigation into Nigel Stepney, a British-born senior mechanic, who Ferrari claim has been involved in the unauthorised leaking of information and an alleged attempt to sabotage their racing cars.

Stepney, who has denied the allegations and claims that he is the victim of a Ferrari "dirty tricks" campaign, was dismissed early yesterday. His lawyer has said that, when he returns from holiday this week, he will hold a press conference in Italy at which he will demonstrate his innocence.

McLaren would not confirm Coughlan's identity, but issued a statement in which they said that they had become aware yesterday that a "senior member of [our] technical organisation" had received a package of technical information from Ferrari at the end of April.

The affair has the potential to cast a long shadow over Hamilton's glorious debut season. Depending on the outcome of the investigations in Italy and Britain, legal challenges could determine the winners of the drivers' and manufacturers' championships. A spokesman for the FIA, the sport's governing body, said last night: "We have received information on this matter, which we are examining."

The scandal comes as Hamilton, who has finished each of his first eight races on the podium and won two grands prix in a record-breaking start to his Formula One career, prepares to drive in front of thousands of British fans at Silverstone next weekend.

At the heart of the case is highly secret technical information about car performance that results from millions of pounds' worth of research. Ferrari believe that the improvement in McLaren's performance after the Spanish Grand Prix on May 13 is consistent with the apparent leaks at the end of April.

In the first four races of the season, Ferrari held a decisive advantage over McLaren, but this was overturned in the subsequent races in Monaco, Montreal and Indianapolis. Last weekend, in the French Grand Prix at Magny-Cours, Ferrari were back on top, scoring a one-two via Kimi Raikkonen and Felipe Massa.

Even by Formula One's extravagant standards, yesterday was a day to stretch credulity as details of what could be one of the biggest secrets scandals the sport has known emerged through a series of revelations by Ferrari and McLaren Mercedes.

It had been apparent for ten days that Ferrari were investigating Nigel Stepney, their disaffected former race and test technical manager, who the Scuderia allege had been involved in an attempt to sabotage Ferrari's racing cars, six days before the Monaco Grand Prix at the end of May.

But yesterday the Italian team made a new claim against British-born Stepney, alleging that he had also been involved in leaking secret technical information to McLaren. It then emerged last night that the individual who was allegedly in receipt of that information was Mike Coughlan, who has been chief designer at McLaren Mercedes since 2002. The pair had worked together at Benetton in the 1990s and later at Ferrari.

Ferrari had earlier issued a statement in which they said that they had instigated legal action against a senior McLaren engineer, both in Italy and in England, and linked the developments at McLaren with their investigation into Stepney. "Ferrari announces it has recently presented a case against Nigel Stepney and an engineer from the Vodafone McLaren Mercedes team with the Modena Tribunal, concerning the theft of technical information," the team statement said. "Furthermore, legal action has been instigated in England and a search warrant has been issued concerning the engineer. This produced a positive outcome. Ferrari reserves the right to consider all implications, be they criminal, civil or of any other nature, according to the applicable laws."

McLaren had earlier disclosed that they became aware yesterday that what they called a "senior member of its technical organisation" was the subject of a Ferrari investigation regarding the receipt of technical information. Their statement said: "The team has learnt that this individual had personally received a package of technical information from a Ferrari employee at the end of April. Whilst McLaren has no involvement in the matter and condemns such actions, it will fully cooperate with any investigation. The individual has, in the meanwhile, been suspended by the company pending a full and proper investigation."

Earlier in the day as the teams prepare for the British Grand Prix at Silverstone this weekend, Ferrari said they had dismissed Stepney after the completion of an internal investigation. The engineer is a widely respected figure within Formula One and played a key role in Ferrari's supremacy during the Michael Schumacher era.

It is understood that the Ferrari investigation into Stepney initially centred on an alleged attempt to sabotage their cars after the discovery of a mysterious white powder in the fuel tanks of two Ferraris as they were being prepared for the Monaco Grand Prix.

Stepney, who is on holiday in the Philippines, has protested his innocence, calling the allegations against him a "dirty tricks campaign".

"I have confidence I'll be cleared by the legal process that is now taking place," he was quoted as saying ten days ago. Sonia Bartolini, his lawyer, has said that he will hold a press conference to prove his innocence.