By Will Smale Business reporter, BBC News

An increasing number of firms now make biodegradable packaging

As Sainsbury's becomes the latest firm to introduce biodegradable packaging or carrier bags, the major retailers are falling over themselves to trumpet their green credentials.

The news that Sainsbury's is to start selling more than 500 of its own-brand products in compostable packs comes just days after Ikea said it is to replace all its carrier bags with a biodegradable version.

Ikea has further started charging for its bags; and Tesco, which is also introducing biodegradable bags this month, is offering loyalty points to customers who reuse their old bags, even if they are from a rival store.

But are the UK's retailers really committed to extensive long-term environmental improvement, or are such moves on bags and packaging simply window dressing?

Zero packaging

Environmental charity Waste Watch said it welcomed Sainsbury's announcement on biodegradable packaging, but added that it wished the supermarket and its rivals would go one stage further.

Tesco is introducing biodegradable carrier bags this month

"Our key point is that most people who buy organic food don't actually want packaging at all," said Waste Watch's head of strategy, Jim Fielder.

"They want to buy it loose. We'd like to see supermarkets provide more food, such as fruit and vegetables, without any packaging whatsoever."

Other environmental pressure groups such as Friends of the Earth cautioned that while moving in the right direction, Sainsbury's and its retail rivals still have a long way to go before they can be fully viewed as green companies.

The pressure groups stress that packing and carrier bags are just one area in which they want supermarkets to improve their environmental credentials.

Friends of the Earth says it also wants to see:

• Improved prices for farmers, both in the UK and overseas, so they can meet higher environmental standards
• A reduction in food miles through increased local purchasing and direct delivery to stores
• An end to the construction of out-of-town stores which require shoppers to use their cars to get there

"It makes good business sense for Sainsbury's and they are responding to customers, but it is actually a very welcome initiative," said Friends of the Earth senior campaigner Vicky Herd.

HAVE YOUR SAY I hope the supermarkets will do this properly Harry Lee, England Send us your comments

"It's a small number of lines - if they say what they are doing is 500 lines, potentially they sell 40,000, so it's a small drop in the ocean at the moment.

"But it'll show that compostable packaging can work and that people can do it in their homes, they can put it in their wormery and their compost.

"And we want Sainsbury's to do far more to deliver packaging that is either recyclable or compostable or just reduce packaging."