Supermarkets mislead shoppers with 'dubious' special offers, Which? says Which? investigated the price of 700,000 items on sale in Tesco, Sainsbury's, Asda, Ocado and Morrisons over the last year. It uncovered a range of tactics that supermarkets use to make shoppers believe they are getting a better deal than they are when they do their weekly shop. For example Which? found that some retailers increase the price of a product for a few days before then "discounting" the product at a lower price for weeks. It named Tesco blueberries as one example. Which? also found that supermarkets increase the price of an individual product - such as a pot of yoghurt - when that product becomes part of a bulk "multibuy" offer. The effect of the price increase makes the "multibuy" deal seem better value, when in fact shoppers are paying more per item than they previously had been. Meanwhile some supermarkets exaggerate the old, higher price of a product to make it seem cheaper when the price is lowered. For example Which? said that Asda used this tactic with Aquafrash Milk Teeth Toothspaste. It said the supermarket claimed the "old" price prior to a cut was £1.74 when in fact it was £1.18. In a survey of shoppers, Which? found that almost two fifths of consumers said that special offers encourage them to buy products that they don't really need. A third had bought a special offer they'd regretted. A quarter of people said they try to avoid end-of-aisle displays so that they don't get sucked into buying special offers. In response to the survey, supermarkets said that they always strive to offer shoppers the lowest prices. Tesco and Asda said that they occasionally "make mistakes" on their pricing, and Sainsbury's said that it "would never seek to mislead" its shoppers.