Used car data provider CAP has been put up for sale by Emap for an estimated £150 million.
Emap, which is now owned by Guardian Media Group and Apax Partners, bought CAP for £20 million in 1994.
It is believed Emap has been approached by an interested party in purchasing the price guide company.
The Guardian said the sale of CAP will help Emap to pay off its debts.
Guardian Media Group, which also publishes MediaGuardian.co.uk, and Apax bought Emap in December 2007 for about £1bn, with both companies subsequently forced to write down the value of the investment.
Mike Hind, CAP communications manager, said: "We’re a month away from bringing Black Book Live to market and the biggest investment in CAP for many years is already under way so, in truth, everyone is too busy to be distracted by stories of a possible sale.
"Yesterday’s announcement of the strategic restructure of the old Emap to form ‘Top Right Group’ and the rebranding of our division from Emap Insight to ‘4C’ means our customers will certainly start to see some branding changes but day to day operations will not be affected.
"The fact is that, under private equity ownership, a business is technically ‘up for sale’ if the right price is offered at almost any point. We’re used to stories like this and they never divert us from the job in hand."