Asda's decision to join Tesco and Waitrose in raising the price of its own label milk has had little impact on its position as the UK's cheapest supermarket, according to The Grocer 33's latest survey.

Both Asda and Morrisons have boosted the cost of a four-pint bottle of milk by 11p this week to £1.11. However, our report also shows that Somerfield and Sainsbury are still standing firm at £1.

The cost of this week's 33-item basket at Asda came to £37.73, which is just 7p cheaper than Tesco, which was once again in second place this week.

The top two cheapest supermarkets were matching each other for price on 32 of the items on our list, with Asda being cheaper due to a special offer on its Dolmio Bolognese Original sauce.

Last week we reported that the retail price of white seedless grapes had risen dramatically since their last appearance on The Grocer 33 list in March. What a difference a week makes - our latest report shows that the per kg price of white seedless grapes has plummeted over the past seven days from an average of £3.02 to £2.43.

Tesco, Asda and Sainsbury have all slashed a pound off their prices, with all three now selling the kg for £1.98 compared with £2.98 last week. Meanwhile, Morrisons had reduced the price of its white seedless grapes by 50p.

Sainsbury claimed the week's third-cheapest shopping basket thanks to its cheaper milk and grape prices. Its receipt was 50p dearer than Tesco's at £38.30, and a comfortable 57p cheaper than Morrisons, which was once again ranked in fourth place at £38.87.

Our findings reveal that Sainsbury was beating Morrisons for price on eight of the 33 items on our list, and was cheaper for a selection of its own label fresh foods such as pork sausages and penne pasta. Oranges, courgettes were also cheaper.

Somerfield and Waitrose were in fifth and sixth places respectively. Somerfield's basket was £42.82, while Waitrose was £1.77 more expensive for the same basket of goods at £44.64.Asda Eastgate shopping centre, Basildon

0 Our mystery shopper was able to collect a full 33-item basket of goods when she visited Asda's Eastgate store in Basildon. She spotted four deals on items from The Grocer 33's list, including Dolmio Bolognese sauce, Robinson's whole orange, own label apple juice and Doritos corn chips cool original flavour.

We visited on 23 June 2006 at 08.40. Our shop lasted 48 minutes. Time spent at the checkout was 1 minute.

tesco Knocknagoney Road, Belfast

0 Own label cheapest peach slices and McCain hash browns were not sold at Tesco's Knocknagoney Road store in Belfast, which meant that our shopper was only able to collect 31 items. He spotted a half-price offer on white seedless grapes and a two for £2 offer on Mars Bars and Doritos corn chips cool original flavour.

We visited on 23 June 2006 at 18.45. Our shop lasted 80 minutes. Time spent at the checkout was 5 minutes 35 seconds.

sainsbury Wyndhan Street, Newport

0 Sainsbury's Newport store in Wales was the winner of this week's Top Store Award and provided all 33 items on our shopper's list. She was able to take advantage of three deals including a two-for-£1 offer on whole cucumbers, two-for-£2 on both Doritos corn chips cool original flavour, and a two-for-£2 offer on Mars bars 6-pack.

We visited on 23 June 2006 at 12.13. Our shop lasted 53 minutes. Time spent at the checkout was 4 minutes.

morrisons Billacombe Road, Plymstock

0 Morrisons' Plymstock store in Plymouth just missed out on a full 33-item basket as it only stocks Mars bars in a 9-pack rather than the 6- pack that our current shopping list requires. Our Morrisons shopper only spotted one deal on Robinsons Whole Orange drink as she made her journey around the store.

We visited on 23 June 2006 at 10.30. Our shop lasted 80 minutes. Time spent at the checkout was 6 minutes 24 seconds.

somerfield Standish, Lancashire

2 Somerfield's Standish store in Lancashire only provided 29 products on our list. The store does not sell Amoy Straight to Wok noodles or own label croissants in a four-pack It was out of stock of loose courgettes and Doritos corn chips cool original flavour. Our shopper noted a bogof on Robinsons whole orange.

We visited on 23 June 2006 at 16.20. Our shop lasted 50 minutes. Time spent at the checkout was 3 minutes.

waitrose Sheen Road, Richmond

1 Waitrose's Sheen Road store in Richmond provided our shopper with 31 of the 33 items this week. The store was out of stock of its own label thick pork sausages and our shopper was informed that it does not stock own label rubber gloves in a single pack.

We visited on 23 June 2006 at 11.55. Our shop lasted 48 minutes. Time spent at the checkout was 4minutes.Who we visited

Co-op Springfield Road, Elburton, Plymouth

Booths Berry Lane, Lancashire

MACE Newton Park, Belfast

Spar London Road, Isleworth

BEST ONE Ditton Hill, Surrey

How they performed

Booth's small Berry lane store in Lancashire was the only store to provide our shopper with all ten of the Top Up Shopping items on our list this week.

The store also performed highly in terms of customer service. Our shopper was impressed by its layout and presentation, and by the fact that all her goods were packed for her by the till assistant.

A couple of the products on our list have been switched this week. Our shoppers are now collecting Tetley tea bags in a 250g pack as opposed to 500g, and the cheapest own label butter block has been replaced with a branded alternative.

The cost of our shopping at Spar's London Road store was £10.02. The store narrowly missed out on a full basket as it does not stock Stella in the size we requires. However our shopper did spot a promotion on a pack of six for £5.

Mace's Newton Park store in Belfast does not have a licence to sell alcohol so our shopper had to go without his Stella. The store was also out of stock of Tetley tea bags and at 39p had the highest price for a Mars bar.

Bacon prices appear to differ wildly across this week's five stores. The most expensive was at Mace for £2.39, while Best-one's Thames Ditton store was selling a 6-rasher pack for 99p. The store also did not stock Stella in 440ml cans. Our shopper had a little difficulty locating some products and described the interior as cluttered. However, staff were eager to help and packed her bags

Eight products were available at Plymouth and South Devon Co-operatives' store at Elburton in Plymouth. Bacon was out of stock and the store does not sell Whiskas catfood in jelly.