The FIA has revealed that emails between McLaren drivers proved that the British-based team used information leaked from title rivals Ferrari.
McLaren were stripped of their 2007 constructors' points and fined £49.2m after a hearing into "spygate".
The affair began in July when a 780-page dossier of Ferrari data was found at the home of now-suspended McLaren chief designer Mike Coughlan.
He received the data from Ferrari's ex-chief mechanic Nigel Stepney.
In a 15-page document, the FIA said emails showed that test driver Pedro de la Rosa and fellow-Spaniard Fernando Alonso had been aware of the Ferrari data.
"The emails show unequivocally that both Mr Alonso and Mr de la Rosa received confidential Ferrari information via Mike Coughlan.
"Both drivers knew that this information was confidential Ferrari information and that both knew that the information was being received by Coughlan from Nigel Stepney," the report states.
In what is being viewed as the most damning section of the report, the FIA has published an email exchange between De la Rosa and Alonso.
"All the information from Ferrari is very reliable," De la Rosa wrote to Alonso on 25 March in an exchange about the Ferrari's weight distribution.
"It comes from Nigel Stepney, their former chief mechanic - I don't know what post he holds now.
"He's the same person who told us in Australia that Kimi (Raikkonen) was stopping in lap 18. He's very friendly with Mike Coughlan, our chief designer and he told him that."
McLaren has refused to comment on the FIA's revelations, published on the eve of the Belgian Grand Prix in Spa.