The Carbon Disclosure Project (CDP) is to extend its collaboration with corporate giants. It will help them assess greenhouse gas emissions and create a single standardised approach for climate change information throughout their supply chains.

It aims to help customers and suppliers work together to develop strategies to reduce their carbon footprints.

Tesco and Unilever joined the CDP Supply Chain Leadership Collaboration (SCLC) last October and PepsiCo is among the latest batch of large companies to join its ranks. Each SCLC member has selected up to 50 suppliers to work with them on a pilot project, which will refine the process before it is rolled out in May. Tesco chief executive Sir Terry Leahy said the CDP initiative had "a simple aim to bring together major retailers and key brands, so that we can understand, report and reduce carbon emissions within the supply chain". He added: "I very much hope that firms who supply us and our competitors will consider being part of this venture."

Ian Midgley, senior vice-president supply chain for Unilever, said the firm had been tackling the impact of its own operations on the environment for some time. But he added: "We want to continue to develop our understanding of greenhouse gas management across our supply chain. Collaboration with the CDP and other firms with similar aims should accelerate learning and leverage expertise in this area."