Fancy a pound off your half litre of Ben & Jerry's Cookie Dough ice-cream? Just hand your mobile phone to the cashier and she can scan a unique barcode you have downloaded on to your screen to get your discount.

Well she can if you live in Hillsborough, New Jersey, and buy your groceries at ShopRite. That's where Unilever, the Anglo-Dutch consumer goods giant, is testing the "Holy Grail" of marketing.

Shoppers can visit a special website and download discount vouchers direct to their mobile phones. These are then scanned, the discount applied and the offer barcode deleted at the checkout.

The US trial will run for four weeks but Unilever - which also owns Hellmann's mayonnaise, Dove soap and Lipton tea - hopes it will open the way to much greater development.

Many firms already offer printable discount coupons over the internet and a number have tried sending offers to mobiles. But until now these have needed long numbers to be entered at the checkout. Unilever is the first major player to test scannable barcodes for discounts.