Labonte was released when Petty Enterprises announced that it is negotiating with Gillett-Evernham Motorsports to field its flagship No. 43 car next season.
"In over 15 years of racing in the Sprint Cup Series, I can't remember a time when the sport's landscape looks as it does today," Labonte said in a statement. "Saying that, Petty Enterprises and I had serious and very sincere discussions about what was best for myself and everyone involved at Petty Enterprises moving forward. I am ready to explore all opportunities."
Labonte, 44, the 2000 champion, had driven for Petty since 2006 but has decided not to retire, and Petty Enterprises becomes a single-car entity.
Labonte has won 21 times in 546 career races.
"Bobby is a true champion who never failed to give everything he had when he was behind the wheel," Richard Petty said.