A police raid - instigated by Ferrari - on the British home of McLaren chief designer Mike Coughlan has found documents belonging to the Italian team.

Ferrari, who claim that 'a large amount of technical information' had been stolen from their Maranello factory, believe that their British engineer Nigel Stepney, whom they sacked on Tuesday, had illegally supplied the documents to Coughlan.

'We have proof that Stepney had been supplying technical information to a McLaren employee and we found evidence of that fact in his home,' a Ferrari spokesman declared.

'We are talking about a lot of information being given to a prominent McLaren engineer. We are not talking here about rumours or speculation.'

Ferrari president Luca Cordero di Montezemolo added yesterday that 'it was an incident of unheard of seriousness'.

McLaren would not confirm Coughlan's identity, but he was suspended on Tuesday.

The team, who are leading the constructors' championship, said that they had become aware that a 'senior member of our technical organisation' had received a package of Ferrari technical information at the end of April.

McLaren insisted yesterday that their cars did not contain any Ferrari-related alterations.

They invited the International Automobile Federation (FIA) to conduct a full review of their cars 'to satisfy itself that the team have not benefited from any intellectual property of another competitor', reported the Associated Press.

At the heart of the case is highly secret technical information about car performance that results from millions of dollars worth of research.

Ferrari believe that the improvement in McLaren's performance after the Spanish Grand Prix on May 13 is consistent with the leaks at the end of April, reported The Times of London.

In the first four races of the season, Ferrari held a decisive advantage over the British team, but this was overturned in the subsequent races in Monaco, Montreal and Indianapolis.

Last Sunday, in the French Grand Prix, Ferrari were back on top, scoring a one-two via Kimi Raikkonen and Felipe Massa.

As a mood of crisis threatened to envelop the sport, the FIA confirmed: 'We have received information on this matter, which we are examining.'

But the governing body will be powerless during any criminal investigation either in Italy or Britain, while Ferrari could launch a separate legal case that would determine the victors of both the Drivers' and Constructors' World Championships in the courts.

That could ruin Hamilton's sensational debut season for McLaren. He leads the drivers' standings on 64 points, a 14-point margin over teammate and defending champion Fernando Alonso.

This highly embarrassing development for McLaren will almost certainly take the gloss off Hamilton's efforts to win the British Grand Prix in front of home fans at his first attempt on Sunday.

Stepney was the cornerstone of Michael Schumacher's seven world titles with Ferrari.

Coughlan, 48, is, to a large degree, responsible for the car Hamilton has driven to the top of the drivers' standings.

The duo are two of the most respected technical figures in the sport and worked together at Lotus in the 1980s and at Ferrari in the 1990s.

Speaking to The Times of London from the Philippines, where he is currently on holiday with his wife, Stepney claims he is innocent and is the victim of a smear campaign.

'I have confidence I'll be cleared by the legal process that is now taking place,' said the 47-year-old.

Ferrari blame him for the mysterious powder found on the gas tanks of Massa and Raikkonen's cars on May 21, six days before the Monaco Grand Prix.

The parts were replaced and the powder sent to the police for examination.