Tesco is lagging further behind Asda than ever in The Grocer 33 shop having this week recorded the fourth-cheapest basket for the fourth week in a row.

Once again Asda was the cheapest, with a basket cost of £39.78, with Sainsbury's the second-cheapest for the third week in a row at £40.61. Morrisons was the third-cheapest at £41.09 and Somerfield fifth-cheapest at £44.95. Waitrose was once again the most expensive retailer, with a basket cost of £47.85.

Tesco's £41.39 basket seemed to have been affected by the higher prices of its fresh produce. The price of a single orange at Tesco was 11p more than at Asda and Morrisons, for instance, with a kilo of closed cup mushrooms 10p more expensive than at Asda and a kilo of loose parsnips 40p more expensive. The price of its own- label celery shot up 51% while the price of a kilo of new potatoes at Sainsbury's rocketed by 54%.

Elsewhere, however, Sainsbury's consolidated its position as the second-cheapest retailer. It appeared to have benefited from several small but significant price cuts this week including 10p off the price of a kilo of closed cup mushrooms, 23% off the price of loose broccoli, and a 33% reduction in the price of its own label Brussels paté.

Asda, meanwhile, has increased the price of Marmite by 12p since last week and hiked the cost of four pre-packed baking potatoes by 46%. Morrisons raised the price of its own-label dried spaghetti from 27p to 28p.

Somerfield continued to follow the pattern it set last week and slashed the prices of four items, cutting the price of Amoy Straight To Wok medium noodles by 30%, for instance. Our shopper noted no fewer than six offers including two-for-£2 on Dolmio bolognese original sauce and two 2-litre bottle of Coca-Cola for £2.30.

Morrisons also offered a variety of promotions, with our shopper listing a three-for-£1 deal on Heinz Baked Beanz and two-for-£2.30 on 2-litre bottles of Coca-Cola.