Although the Maranello-based outfit has refused to comment on the situation, a report in Italian newspaper Il Giornale said that Sassi's departure had been prompted following direct intervention from president Sergio Marchionne.

It is unclear if he has left the company completely, or has been moved to another role within the Fiat group.

Sources have suggested that Sassi left the team only in the last few days, and the move has created some shock because Ferrari had made good progress with its power unit this season.

Sebastian Vettel is leading the championship by 14 points over Lewis Hamilton, and many in F1 believe that there is now very little difference in power terms between the Ferrari and Mercedes engines.

Furthermore, Sassi's departure comes ahead of suggestions that Ferrari will introduce a heavily upgraded engine at the British Grand Prix which is said to utilise some technical innovations to deliver a good boost.

Vettel himself deflected questions on the impact of Sassi's departure when asked in Austria on Thursday.

"I don't know what you are referring to," he said. "It is better you ask a little bit higher up."