ING branding has been removed from Renault cars ahead of the Singapore GP
Renault have been hit by the news that title sponsor ING will end its contract with the Formula 1 team immediately.
The Dutch-based financial group planned to pull out at the end of the season but will now leave four races early.
The move follows the race-fixing scandal that resulted in a suspended ban for the former world champions.
Renault, who have pledged to stay in the sport despite the bad publicity, had already lost the backing of Spanish insurance firm Mutua Madrilena.
It asked for its name to be removed from Renault's cars on Thursday.
ING was the largest sponsor on Renault's books, providing more than half their total sponsorship revenues according to some estimates.
A report by industry monitor Formula Money earlier this year put ING's contribution to the sport at some $86m (£53m) last season, with $65m (£40m) going to Renault.
"In light of the verdict of the World Motor Sport Council of 21 September 2009 concerning the events that occurred at the 2008 Singapore Grand Prix, ING will terminate the contract with Renault Formula One with immediate effect," the company said.
"ING is deeply disappointed at this turn of events, especially in the context of an otherwise successful sponsorship."
Mutua Madrilena announced earlier on Thursday they had withdrawn their sponsorship from the team for similar reasons.
Alonso will continue to receive the backing of Mutua Madrilena
The company said the decision would have no impact on its sponsorship contract with Spain's double world champion Fernando Alonso, who is expected to move to Ferrari for 2010.
"Mutua Madrilena believes the conduct of the relevant people in the team was of extraordinary seriousness and not only compromised the integrity of the sport but also put the physical safety of spectators, drivers and circuit personnel at risk," the company said in a statement.
"This could affect the image, reputation and good name of the team's sponsors."
Renault were given a two-year suspended ban from Formula 1 for their role in fixing last year's Singapore Grand Prix.
The FIA, the sport's governing body, also banned ex-Renault boss Flavio Briatore for life and suspended former engineering head Pat Symonds for five years for ordering Brazilian Nelson Piquet Jr to crash.
All three individuals implicated in the scandal have since left Renault, but the changes have arrived too late to save two of the team's key sponsorships.
Alonso, who won the Singapore Grand Prix after the safety car was deployed, was cleared of any involvement.