Nigel Stepney, the former Ferrari employee accused of leaking information to McLaren, said on Thursday he is "surprised" by the actions of the Italian team and again denied any wrongdoing.
Ferrari have dismissed former technical manager Stepney and taken legal action in Italy against him and a McLaren employee "regarding the theft of technical information".
Italian news service ANSA said Stepney, a 47-year-old Briton, had rejected the accusations after arriving back in Italy following a break in the Philippines.
Police from Ferrari's home base in Maranello have also told Stepney he is being investigated for "various crimes", ANSA said, adding that two other people are also being probed.
McLaren, who have suspended a senior employee widely identified in the media as chief designer Mike Coughlan, have assured the Italian team that no information has been incorporated into their cars.
They have asked the governing FIA to inspect their vehicles to prove that is the case.
Italian media said Stepney's Italian home had again been searched on Thursday and that he had been in dialogue with lawyers.
McLaren are 25 points ahead of Ferrari in the constructors' standings with British rookie Lewis Hamilton leading double world champion Fernando Alonso by 14 points before Sunday's British Grand Prix, the ninth round of the season.
Formula One supremo Bernie Ecclestone has said McLaren drivers Alonso and Hamilton will not lose championship points as a result of the 'spying' scandal.
