A leading Formula One mechanic is being investigated by police after allegations that he attempted to sabotage two Ferrari racing cars. Nigel Stepney, who earns £750,000 a year as Ferrari’s head of team performance development, is alleged to have interfered with the fuel system of cars driven by Felipe Massa and Kimi Raikkonen.

Mr Stepney, from Warwickshire, was reported to the Italian police after a mysterious white powder was found in the petrol tanks only days before the Monaco grand prix.

He was passed over for promotion earlier this year and is reported to have been looking to move to a new team. Since the mysterious powder was discovered, the Ferrari team’s performance has fallen in the past three grands prix.

The world of Formula One was stunned yesterday after Ferrari confirmed it had held an investigation into Mr Stepney, 47. Although the sport is famous for shenanigans between teams, with fines for cheating and prosecutions for selling secrets to rivals, no one has previously been investigated for trying to sabotage their own cars.

A criminal investigation into the alleged sabotage has been started by the district attorney in Modena after he received evidence from the internal inquiry held at the Ferrari team factory in Maranello, northern Italy.

Luca Colajanni, a Ferrari spokesman, told The Times: “Ferrari can confirm that we have brought an action against Nigel Stepney and that there is an internal disciplinary procedure against him.”

The investigation into Mr Stepney is being seen as a sign that since the retirement of Michael Schumacher, its star driver, and several other key team members, Ferrari is losing the cohesion that made it such a formidable force.

Mr Colajanni dismissed such talk. “This is a sign, if the investigation is confirmed, that someone has lost his team spirit because he is not happy with the choices made by the team management. It is not correct to say the team is falling apart.”

Mr Stepney was believed to be on holiday in Asia yesterday with his Brazilian wife and their baby.

After trials at Coventry City as a schoolboy goalkeeper, he started his career in motorsport as a 16-year-old apprentice mechanic at the Broadspeed Touring Cars outfit at Southam, near Rugby. He joined Ferrari 13 years ago and had worked closely with Schumacher until the most successful driver in Formula One history retired at the end of last year.

However, despite the success of the past decade Mr Stepney’s relationship with Ferrari turned sour when he was overlooked for promotion He told Autosport magazine: “I’m not currently happy with the situation within the team – I really want to move forward with my career and that's something that’s not happening right now. Ideally I’d like to move into a new environment here at Ferrari, but if an opportunity arose with another team, I would definitely consider it.”

This season Ferrari started well, with a win for Raikkonen in Australia and then two for Massa in Bahrain and Spain. But since Monaco at the end of last month, where Massa finished third and Raikkonen eighth, the team has slipped behind the McLaren Mercedes cars of Lewis Hamilton and Fernando Alonso.