At a time when retailers are battling to be greener and more energy-efficient, carrier bags have become the public face of their efforts. The Grocer 33 Online - our quarterly online delivery version of the usual weekly survey - now has a greater focus on the number of carrier bags used for the deliveries, as well as assessing the standard of availability and customer service.

The environmental message seems to be getting through to the more bag-efficient retailers. But for some - and we're looking at you Asda and Tesco - the response is rather dismal.

Three months ago, 53 plastic bags were used by the retailers to deliver 158 items. In this latest survey, 48 bags were used to deliver 158 items, with Tesco and Asda increasing the number of bags used.

Though Asda delivered two more items than Sainsbury's, you have to wonder why it required eight extra bags. Sainsbury's has reduced the number of bags from 11 to six. It must also be applauded for announcing it wants to be the first major UK retailer to convert 20% of its online delivery fleet to green electric vehicles by September 2008.

All our shoppers said the websites were simple to navigate, although our Asda.com shopper was frustrated when he typed in 'apples' and many unrelated products were shown.

Asda once again offered the cheapest delivery charge at £4.75 but was up on the £3.99 it was charging three months ago.

Earliest delivery times are now generally two days later, with only Tesco managing to provide a next- day delivery.

All the retailers delivered on time apart from Sainsbury's whose driver arrived 15 minutes late. However, he did phone in advance to apologise.

As our Tesco shopper met the delivery driver, he received a call from Tesco telling him that his delivery would be about an hour-and-a-half late!

The delivery receipts were generally accurate, however. Our Asda shopper was delighted to receive a bonus orange, absent from the receipt. And though Tesco.com had a buy-one-get-one-free offer for the Doritos, our shopper was mistakenly charged for the second bag.

Ocado and Asda delivered the full 33 items - an improvement on their respective totals of 29 and 32 in the previous survey. The other multiples delivered fewer items this time.

WaitroseDeliver, winner in the previous survey, provided 30 products - the lowest number in the survey and three items fewer than last time. It also had five substitutions but they were similar to the products ordered. For instance, Haribo Kiddies Super Mix was provided instead of Haribo Starmix.

Ocado delivered a 240-pack of Tetley tea bags rather than the 160-pack. Asda.com sent the 30p more expensive Cadbury's Heroes in place of the carton of Mars Celebrations but also Jacob's Creek Semillon Chardonnay instead of Jacob's Creek Chardonnay, which was 49p cheaper. The Jonagold apples were also replaced by the pricier Gala variety.

Our Tesco shopper may well have lost a night of peaceful sleep as Radox Herbal Bath Sleep Easy was substituted by Radox Herbal Bath Muscle Soak. Tesco quiche lorraine was unavailable so a Sutherland quiche lorraine was substituted. Mars Celebrations was out of stock and Haribo Starmix was unavailable. Only our Sainsbury's to You shopper received no substitutions.

The quality of customer service was good, however. Our shoppers reported that their delivery drivers were as polite and helpful as in the previous survey.

The Waitrose driver even offered to help our shopper carry the bags inside, and both Tesco and Asda's drivers were well-presented. The Sainsbury's driver apologised for the late delivery and impressed our shopper with his manners.

Not only did Ocado's Brighton driver unload the bags with care, he also enthusiastically explained the receipt and substitution system. So full marks for service.

The challenge must now be to reduce the number of carrier bags. Retailers - you have three months.