Sainsbury's decision to launch a 'traffic-light' system to illustrate the sustainability of the fish it stocks has met with a mixed response from pressure groups.

The retailer is planning to colour-code fish products with red, amber or green symbols according to their sustainability. However, the indicators will appear only on the supermarket's website and at fish counters, and not on packaging.

Greenpeace welcomed the move, saying it was the supermarkets' responsibility to ensure that fish is sustainable. 'The success of the scheme will be down to how Sainsbury's publicises it,' said a spokesman. 'I hope it promotes it properly in-store.'

But some campaigners believe the scheme does not go far enough and may confuse consumers. A spokeswoman for Sustain said: 'People may not understand or notice the labelling. It would be better to get rid of the endangered and fragile stock altogether.'

A Sainsbury's spokeswoman said it aims to remove all red-rated fish from its counters and stock only green-rated where possible. In January, Asda promised to improve the sustainability of its fish supplies after it was ranked bottom in Greenpeace's annual poll of supermarkets' fisheries policies.

The retailer suffered a wave of negative publicity and withdrew four species from sale - ling, huss, skate and Dover sole. Sainsbury's has already introduced a 'traffic-light' nutrient labelling system for its own-label food products.