Asda is the UK's cheapest supermarket for the third week in a row. In a tight race, Asda's basket price of £46.42 came in barely cheaper than Somerfield's total of £46.86. Tesco was third at £47.24, or 1.8% more than Asda, followed by Morrisons, Sainsbury's and Waitrose respectively,

Somerfield's second-place finish this week was driven by a sale on its lamb chops - at £6.49 per kg almost 40% cheaper than Morrisons, the closest competitor on that product.

While the drought is expected to result in higher prices for British fresh produce, there was little impact on the items in our shopping basket. Somerfield raised the prices of its carrots by 7% to 72p per kg, but the other supermarkets held their prices. There was no change this week in the prices for cucumbers.

Prices on the frozen vegetables in our basket were also stable this week, although Somerfield put up the price of Birds Eye garden peas by 15% to £1.40, while cutting own-label mixed vegetables by 10p to 82p

There were some price cuts on imported fruit. Waitrose reduced the price of its bananas by 4% to 84p, making it the cheapest on that product. And both Sainsbury's and Tesco offered red seedless grapes at £1.98, down from £2.49 and £2.48 respectively.

In the bakery category, five of the six supermarkets raised the price of Soreen's fruited malt loaf by at least 6p each. Sainsbury's and Somerfield made the highest increases on that product at 17% and 16% each. Waitrose, which was previously the most expensive supermarket for the Soreen loaf at 69p, did not change its price.

Our mystery shopper at Sainsbury's noted the highest number of promotions on items in this week's basket. Sainsbury's had offers on six items, or almost a fifth of the 33-item shopping basket. Most notable were Spanish grapes at 50p off, regularly £2.48, and a bogof on tubs of own-label Brussels pâté.

Waitrose was next highest with offers on five of the 33 items.