Asda has taken flak this week after launching a two-for-£2 promotion on milk. But just days after we crowned Asda the decade's cheapest retailer, it's no surprise to see the price cuts coming out again. Asda knows the promotion will drive milk volumes up - by 5%, it estimates. And if shoppers come to the store for milk, they'll buy the rest of their groceries too, so it's an important footfall driver. But the tenor of recent advertising has changed in a subtle, but significant, way as the supermarket emphasises its ethical stance. It wants everyone to know its farmers receive a 1p bonus for each litre of milk they supply. It's sure to play well with consumers, who feel good about supporting farmers while getting a bargain. And our analysis of dairy prices also shows that, although its prices are falling the fastest of the multiples (down 5.4%), while Tesco's is going the other way (up 3.9%), dairy prices at Asda are still the highest of the multiples, while Tesco's are the lowest. So who exactly should be taking the flak, you may well ask?