BHP Billiton is known down under as “the big Australian”, but the mining giant has deep roots in Britain, as became clear yesterday when it started to classify metals by their social class.

Marius Kloppers, the chief executive, described aluminium as a “middle-class commodity”, which is not a reflection of the metal's life in suburbia but its greater consumption by developed economies. Iron ore, copper and steel, on the other hand, are lower class as they are bought in greater quantities by emerging countries.

Mr Kloppers was not trying to ignite a new class war but trying to highlight why BHP is better placed this year than its rival Rio Tinto.

After the $38 billion acquisition of Alcan last year, Rio gets about one third of its earnings from aluminium. As the economies of Europe and North America slow, demand for cans, cars and other aluminium products will fall (the metal's price is already down 17 per cent in the past two months).

By comparison, BHP gets only 6 per cent of its earnings from aluminium and has a bigger exposure to the working-class metals that are used to build infrastructure in China and other rapidly developing economies.

Of course, Mr Kloppers has good reason to champion this class divide. BHP has offered 3.4 of its own shares for each one of Rio's in a takeover deal worth about £70 billion. Therefore, the more that Rio's share price falls against BHP's, the more attractive this deal looks. Rio's shares are trading at three to one at present and BHP is hoping that further weakness will have shareholders flocking to accept its deal later in the year.

However, as with all artificial divisions the situation is not as black and white as Mr Kloppers claims. China consumes about 40 per cent of the world's aluminium, which suggests that the metal is both working and middle class. Also, the price of aluminium could rebound this year as China shuts down its production of the metal. The aluminium smelting process is extremely energy intensive and between 10 and 20 per cent of Chinese production has been mothballed, which could force up prices.

Ultimately, it will not be lower or middle-class metals that decide this takeover battle but bureaucrats in Brussels, who must determine whether the merger of the world's largest and second-largest miners is a concern. Presumably, these bureaucrats represent the upper class in Mr Kloppers' world view.

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