Guardian Media Group is selling its 50.1% stake in Trader Media Group, which owns Auto Trader to its joint venture partner Apax Partners.
The proposed acquisition of GMG’s 50.1% stake follows the original acquisition by the Apax Funds of its 49.9% stake in TMG from GMG in 2007.
The financial terms of the agreement were not disclosed although the deal is thought to be worth about £600m to GMG.
Tom Hall, partner at Apax Partners said: “It has been a pleasure to work with GMG as partners over the past six years in our collective investment in TMG.
“They have played an essential role in the extraordinary transition of AutoTrader from print publisher to pure online marketplace. The deal is subject to regulatory approval.
Trader Media Group had operating profits of £117.8m in the year ending March 2013 on revenues of £251.8m. Pre tax profits were £31.5m.