Tesco has scored a double whammy this week, adding the crown of cheapest supermarket to its Top Store customer service award. The victory is the second in a row for the retailer, which has fought back on prices after a long period of dominance by Asda.

Tesco's basket price of £46.22 gave it a convincing victory. There was massive gap of 94p between it and runner up Asda, which finished with a total of £47.16.

The margin of victory once again came down to promotional pricing as Tesco continued its deep discount on parsnips, offering them at 99p instead of the normal level of £1.88, while Asda maintained its price at the latter level.

Nonetheless, Asda was very competitive. After the promotional price on parsnips was stripped away, Asda was a mere 5p behind Tesco. Comparing the rivals head to head, we continued to see a great deal of price parity, with both offering the exact same price on 24 of the 33 items on our grocery list.

Following Asda was Sainsbury's, which repeated last week's third place finish, this time with a total of £47.40. Morrisons was fourth at £49.13, or 6.1% behind Tesco's total. Somerfield and Waitrose rounded out the list, finishing in fifth and sixth places respectively.

Price changes showed up in several product categories this week. Most notable was a sharp spike in onion prices, with both Asda and Morrisons pushing the price of loose onions up by 16% and 15% respectively, to £0.68 and £0.69 per kilo, their highest prices for the product so far this year.

Celery was another hot spot, with Tesco cutting the price by 20p to £0.44 and Waitrose increasing its price by 18p to £0.69.

We saw price changes in the bakery category yet again, with Asda increasing the price of its in-store bakery wholemeal loaf by 4.1% to £0.76 and Somerfield increasing it by 3.8% to £0.80.

Somerfield also bucked the recent trend of price increases on mushy peas, instead lowering its price by 6p, to £0.17, which also made it the low price leader on that item.