Formula 1 has been thrown into chaos after eight of its major teams said they are now planning to set up a rival championship for the 2010 season.
The threat by members of the F1 Teams Association (Fota) escalates their row with world motorsport boss Max Mosley over his budget cap proposals.
"The teams have declined to alter their original conditional entries to the 2010 F1 Championship," said the teams.
"We've no alternative than to commence preparation for a new championship."
Mosley was insistent on introducing a voluntary £40m budget cap for teams to curtail a "financial arms race" in F1.
But Fota refused to agree to his conditions, prompting championship leader Brawn GP, Ferrari, McLaren, Renault, Toyota, BMW Sauber, Red Bull Racing and Toro Rosso to take their drastic action.
They announced their decision following a four-hour meeting on Thursday night ahead of this weekend's British Grand Prix at Silverstone.