Mr McKevitt says: "After a positive month last time around, Sainsbury's sales were down by 0.2% in the past 12 weeks, with its market share falling back slightly to 15.6%. Meanwhile, Tesco saw sales fall by 0.6%. The UK's largest supermarket recently unveiled its new 'Clubcard Plus' offer which gives subscribers 10% off two large shops each month. Some 1.8 million households made at least two trips to the retailer worth £50 or more in the past four weeks, a number Tesco will be looking to boost through its latest initiative."