AutoTrader Group has decided not to go public, saying it will continue on its rapid growth path as a private company owned by Cox Enterprises and two private equity firms.

“The company has flourished under private ownership,” said AutoTrader spokesman Lou Laste. “We think that’s the best course for us right now.”

In a filing with the U.S. Securities and Exchange Commission on Friday, Atlanta-based AutoTrader said it is withdrawing its registration for a planned stock offering “due to prevailing market conditions.” The Internet car sales company had filed the registration last summer as a first step toward raising up to $300 million in an initial public offering.

AutoTrader has roughly 1,500 employees in Atlanta and 2,500 overall, Laste said. It is about two-thirds owned by Cox Enterprises, the parent company of The Atlanta Journal-Constitution. Other major shareholders are private equity firms Provident Equity Partners and Kleiner Perkins Caufield & Byers.

AutoTrader, which has been on a rapid growth track propelled by acquisitions, reported a 38 percent jump in revenue in 2011, to just over $1 billion. In last summer’s filing, AutoTrader said its profits in the first half of 2012 grew almost 30 percent, to $41.6 million, while sales rose almost 15 percent, to $563 million.