CAP analysts are reporting a 13.5% rise in used values year-on-year and an unusually buoyant last two months, but Glass's maintains the increase is much smaller and the seasonal decline in demand has been in line with expectations.

According to CAP, the rate of price increase has accelerated since the summer as the market defies traditional seasonal trends. Values fell only 3.1% between September and December this year compared with 6.2% last year. Chief economist Mark Cowling said dealers had realised that instead of unloading cars post-August and having to restock in January, it made more sense to cherry-pick the most desirable cars while prices were traditionally lower between October and December.

Glass's editor in chief Arnie Fenn said: 'CAP saw a massive drop in the market in September, but we didn't. They exaggerated the fall in the market and then tried to compensate. It was the wild price fluctuations that CAP printed in September that created the panic situation that held prices down. The market would have been much more stable if they hadn't published a knee-jerk reaction.'