The big four supermarkets have bought forward their Christmas discounting – with alcohol one of their key drivers. Nielsen, the consumer research group, said that the main retailers had started discounting in late September rather than leaving it to the traditional period of the last two weeks of October or the start of November. The development comes after it was revealed that third quarter alcohol sales in the off-trade had been weaker than the on-trade. The move towards a return to alcohol discounting also follows a series of pledges by the supermarkets on the issue. In May, Tesco said it would support a minimum cost on alcohol in response to government proposals designed to combat binge drinking and anti-social behaviour. Asda also promised to stop selling alcohol below cost in what it described as, “a small, but important first step towards creating a new way of selling alcohol in the UK.” However, last week the Walmart-owned supermarket launched a promotion offering shoppers three boxes of selected beers, cider and RTDs for £18. Although not below cost its latest deal leaves little in the way of cost for production. Nielsen figures show that in the four weeks to 2 October the most heavily promoted categories in supermarkets were soft drinks, liquor and confectionary Mike Watkins, a senior manager at Nielsen, said: “We are finding that these sort of promotions started in September.” David Cameron, the prime minister, has also previously pledged to combat the problem. He said: “I think if what you're trying to do is stop supermarkets from selling 20 tins of Stella for a fiver that's what we've got to go after. Where I want to try and help is ending the deep discounting on alcohol. “People going and 'pre-loading', having bought from a supermarket where they were attracted by a price designed to bring them into the store.”