The publisher of the Guardian newspaper says it is selling its stake in a car classified service so that it can focus on investing in journalism.

Guardian Media Group said Tuesday that its 50.1 percent stake in Trader Media Group, which owns Auto Trader, will be sold to private equity firm Apax Partners.

The value of the deal was not disclosed, but Apax acquired a 49.9 percent stake in 2007 for almost 700 million pounds ($1.2 billion).

Guardian Media Group chief executive Andrew Miller said money from the proposed sale will strengthen the company's balance sheet and allow it to invest in its core news publishing business.