Supermarkets have recently been under fire for selling own-brand products that bear a striking similarity to leading rivals. Now they are responding with distinctive new designs, such as a baby's rear. Hugh Aldersey- Williams looks at the bottom line.

Tension has risen in recent years between owners of famous brands and newcomers keen to muscle in on the large markets that they command. Friction has been especially noticeable with supermarket retailers whose own-brand products have often been designed to resemble these brands.

In September, Asda was forced to withdraw its Puffin biscuit after complaints from the leading brand, Penguin. Tesco's own-brand of corn flakes was challenged by Kellogg's in 1996.

Lookalikes can have a devastating impact on brands, according to John Noble of the British Brands Group, set up by manufacturers such as Mars, Procter & Gamble and Nestle largely in order to tackle the issue. Nescafe recently spent pounds 30m changing the shape of the Gold Blend package in order to reassert its distinctiveness in the market. Brand owners also spend thousands in legal fees and invest management time in policing lookalikes. A more insidious effect is the smearing of a brand's reputation if the consumers do not like the lookalike.

Some brands have only themselves to blame. Having failed to register now famous designs in the past, they find they are easy prey to copyists. A quarter of brand manufacturers fail to protect their brands for fear of damaging relations with their retailer customers.

Noble compares the brand lookalike to a marathon runner who just joins the race for the last half-mile. "It is no accident. It is packaging deliberately against the brand in order to exploit the assets of that brand in terms of the innovation that it has made. It is all very deliberate stuff. Lookalikes attack the very essence of branding. They are all about similarity when branding is all about differentiation, distinctiveness and added value."

Now some supermarkets have said they will repent. "Passing off is being knocked on the head, but you will always have sector cues," says Jonathan Sands of the Leeds- based design company Elmwood. The question is whether these visual clues, established in order to help consumers identify a particular product category, are being hijacked for the more specific purpose of drawing attention to cheaper products in that category.

A report published recently by Siebert Head, packaging design consultants, advises cautious innovation. "It is difficult, not to mention risky [for own brands] to be too revolutionary by moving too far away from their category format, as they risk losing vital potential market share," the report says. "This should not mean, however, that they slavishly copy a successful pack design with so little differentiation that it is confused with the original branded product."

The remedy, according to Siebert Head, lies in "structural packaging" - industry jargon for anything more than printed packaging. This is principally how the myriad brands of perfume have differentiated themselves in a crowded market. It may even be how the consumer subliminally distinguishes between whisky and bourbon. The Jif Lemon and the Toilet Duck are more spectacular examples of the art.

The innovation can be small. Elmwood treads the line with packaging for Asda's own-brand baby oil. Launched in November, the packaging resembles a certain well-known brand, with its pear-shaped baby profile. Its unique touch is to mould a buttock cleavage detail into the "bottom" of the bottle. In the event of a legal challenge, Asda will be able to point to this distinctive humorus feature. (If Asda had called its biscuit Guillemot rather than Puffin, the obvious humour might have got it off the charge of copying.)

Sands admits he will not win creative awards for the work. But his client is happy. The packaging, together with a reformulated product, has reversed a previous decline and now allows Asda's own brand to compete directly with branded products. (Other designers believe that achieving these objectives should not be incompatible with top levels of creativity).

A unique shape or other "structural equities" can be supported by other distinguishing features. Hand-lettered graphics are more easily protected than colours, for example. Such features are more readily given legal protection as well as harder to copy in practical terms. Where possible, they should also make it easier for the consumer to release the product from the packaging. "If a structural design offers optimum performance, it has most of the ingredients required to become a market leader in its category," according to Siebert Head.

An example is the packaging of Halford's own brand of motor oils, which is illustrative not only of retailers' healthy new interest in developing their own distinctive brands but also of using them to achieve sector dominance at least in its own stores.

The design solution came in two parts, the form and function of the container, and its appearance and communication. "We thought it was important to use form designers as well as graphic designers," says Chris Forman, Halford's strategic business development manager. "Few retailers, or brand owners for that matter, are aware of when a 3D designer can help." Product designers' expertise in ergonomics, manufacturing processes and materials, and three- dimensional detailing can make the difference not only in terms of user benefits, such as ease of pouring, but also in knowing the tricks that can provide brand differentiation and protection against copying.

Halford's chose the "most progressive" of three design concepts modelled in foam by Gavin Thomson, a product designer at Pentagram. Although not the highest scorer in research, this proposal took advantage of relatively new (and so hard to copy) blow-moulding technology that would lead to the creation of the most distinctive container.

Siebert Head praises retailers like Halfords. They can "well afford to invest in their own strong branding without resort to copy-cat solutions", its report chides. A little extra effort often produces a better result. A straw poll in the editorial offices of Marketing magazine felt that the new, necessarily original packaging for Asda's biscuit better in its own terms - and not only because it is nothing like a Puffin.