A mystery team insider dubbed 'Witness X' provided damning evidence that sealed former Renault boss Flavio Briatore's banishment from Formula One, the sport's governing body revealed on Tuesday.
Former champions Renault were handed a suspended ban from Formula One by the International Automobile Federation (FIA) at a hearing in Paris on Monday for fixing last year's Singapore Grand Prix.
Italian Briatore was banished from the sport indefinitely while Renault's engineering head Pat Symonds was barred for five years. Both men had already left the team.
In documents published on the FIA website (www.fia.com), the world body said a fourth team member had also known about a plot for Brazilian Nelson Piquet Jr to crash deliberately at the race to help Spanish team mate Fernando Alonso win.
The conspiracy had been thought to be limited to Piquet, Briatore and Symonds with the FIA declaring on Monday that double world champion Alonso had not been in the know.
However the FIA said a "whistleblower", revealed by Renault shortly before the FIA's world motor sport council met and identified only to FIA president Max Mosley and certain legal advisers, had also been aware of the plan and had opposed it.
The FIA said Witness X had been "personally present at a meeting shortly after qualifying on Saturday 27 September 2008 when Mr Symonds had mentioned the possibility of a crash plan to Mr Briatore.
"The FIA's advisers were confident Witness X himself played no active role in the conspiracy and that, indeed, he had objected to it and sought to distance himself from it," added the report.
Briatore was earlier quoted by Italian media as being "distraught" at his punishment and threatening legal action against the FIA.
The governing body said there was no evidence anyone else in the team had knowledge of what it called a "secret conspiracy" apart from the four individuals.
It noted Piquet had said Symonds proposed the crash plan to him while the engineer had said the idea came from the driver, and reached no conclusion about who had been responsible.
Symonds was offered immunity by the FIA if he cooperated with the investigation but declined to provide the necessary evidence.
While Briatore shunned the Paris hearing, Symonds wrote to the world motor sport council to express his remorse.
"I would like to acknowledge my role in this incident. I was the one who, when the idea was first suggested to me by Nelson Piquet Jr., should have dismissed it immediately," said the Briton.
"It is to my eternal regret and shame I did not do so," added Symonds, who has been with the same team from the days when it was Benetton and Toleman before that.
"I can only say I did it out of a misguided devotion to my team and not for any personal gain whatsoever. I consider the role I have played in bringing the team to where it is today to be my life's work.
"In a single action I have destroyed the high reputation I have built up during a 33-year career in motor sport," added Symonds.
"On that night in Singapore last year I made a mistake the consequences of which I could never have imagined at the time. For that mistake I can only offer all of you, and all those touched by the action I was involved in, my profound apology."