The boss of Auto Trader has dismissed the threat from RAC Cars to usurp its position as the number one digital market place for used cars in the UK.

Chief executive Trevor Mather said that the RAC is a long-standing, trusted brand, but only as a breakdown company: “You think about them first when you break down on a motorway, but not when I’m about to buy or sell my car.”

In March RAC Cars announced its listings were to be free of charge to dealers and consumers in a bid to “revolutionise” the car classified websites market. At the time it said its site was attracting about 600,000 visitors per month, but would not need to match Auto Trader’s 11 million figure, because it does not have fees to justify.

Then in June RAC Cars' chairman Rupert Keane said it would be the market leader by the end of this year as it passed the 200,000 vehicle listing milestone within 55 days of making its service free. “Our stated aim is to have 500,000 vehicles by the end of this year, something that would make us market leader in terms of volumes,” he said.

Mather warned that RAC Cars announcement it would not charge for listing cars would attract retailers, but if it couldn’t attract a far greater audience of potential buyers, “all you’ve done is reduce the potential response level on every vehicle”. He spoke of the need for a balance between the right volumes of cars on offer and audience figures: “The right way is to balance both: RAC Cars wants 500,000 cars on its site by the end of the year. If it achieves that without an equivalent growth in audience response rates will plummet.”

He also questioned whether the marketing budget would be sufficient to drive sufficient, new amounts of traffic to the competitor site when car marketing was not core to the wider RAC business.

Achieving the 500,000 stock figure would also prove difficult, Mather predicted. “It’s not hard to get to 200,000-250,000,” he said. “It’s really hard to reach 400,000 – 450,000.”

Auto Trader has 350 staff sourcing stock and about 40 that “do nothing but make sure our search experience is as good as possible.”

According to Hitwise, it had a visit share in the car buying market in May of 63.2%.

Auto Trader has an average of 420,000 cars listed on its site, every day.