The recent news that AMG is planning to cull its range to concentrate on ‘real’ AMG models points to a recurring problem in the car industry.

A badge that offers real kudos frequently proves irresistible to marketing types who then want to stick it on anything that moves. The inevitable result: the badge becomes debased and loses the kudos that made it valuable in the first place.

You could call it the ‘Ghia syndrome’. Ford originally put the Ghia badge on the ultimate Granada to lend its flagship some gravitas but, within a few years, there was even a Fiesta Ghia, which meant that Ford then had to invent a Ghia X trim, to be followed eventually by Ultima and Titanium range-toppers.

One might have expected Mercedes to be a bit more discriminating, but its recent policy of ‘access all areas’ meant that everything from the C-class to the ML sprouted a power boost and an AMG badge.

As usual, BMW proved considerably more strategic. The M-badge has been used sparingly: initially only on the M3 and M5, now extended to the M6 and Z4M. The hot 1-series is only known as the 130M, not the M1, because BMW felt, quite rightly, that the performance was not in keeping with such a title.

In terms of sales figures, the success of BMW’s purist approach is self-evident (see table). Even Audi is now seeing the light. After years of so-so performance models, the RS badge is really starting to mean something as demonstrated by its hugely successful RS4, to be followed by the RS6.

Among the volume manufacturers, there is a keen appreciation of what a performance sub-brand could achieve if handled properly. Vauxhall is developing a VXR version of virtually all models in order to give its whole range a halo. It is aware that years of GTi/GSi models has achieved very little, and performance models need a clear identity if they are to have effect.

Ford has also taken the lesson to heart. It is so keen to safeguard its RS badge, it will not even use it at present. The costs of the Fiesta RS and Focus RS prototypes were too high for the bean-counters and Ford would not compromise on performance by making a cheaper RS. They are still scratching their heads about a way of developing a Focus RS – apparently a chipped 250bhp Focus ST wearing the RS badge is considered too cynical.

Ford more purist than Mercedes? Whatever next?

UK sales by country

The sales figures only tell half the story: the other important statistic is that the Audi column consists of one model (RS4), the BMW column of three (M3, M5, M6) and Mercedes of no fewer than eight (C, E, CLS, S, CLK, SLK, SL, CL). So, on average, each AMG version sold less than 40 units in the UK in the first half of 2006.

Clearly less is more: a few clearly focused models will achieve more than a collection of cars given a large engine and a new badge.