The Carbon Trust's launch of ­carbon labels last week was significant. Government-funded, its job is to help companies and the public sector reduce carbon emissions. So its behind-the-scenes development of a c-label ought have been a triumph. A high profile launch was prepared with support from major companies such as PepsiCo, Boots, Innocent, Tesco, Sainsbury's.

Why am I nervous? Let me stress that the food sector's carbon emissions are high and have to be lowered. So there is no disagreement about the goal.

But is it sensible to launch a label on methodology not yet agreed across the food chain? Lifecycle analysis, let alone carbon lifecycles, is complex. The Manchester, Cranfield and Cardiff Universities study for Defra published in December shows that. To rush at c-labels before there's consensus means there is a very real risk of falling at the first hurdle.

Secondly, tackling climate change should not be be a competitive issue, as Sir Terry Leahy stated in his landmark speech on January 17. Even though he made a clear commitment to put carbon labels on Tesco products, he knows everyone has to do this or there is a danger the label could work for one product but not all or, worse, suit some product ranges but not others. Carbon reduction needs to be a shared goal, not just for well-intentioned insiders.

Thirdly, if carbon labelling is to work, it will undoubtedly have to be with a format and logo appropriate for Europe. Nothing is better designed to create confusion than a patchy UK system that is one of several. The FDF and Ben & Jerry's - not my usual stablemates - were right in wanting international standards.

Fourthly, there's a danger of labelling overload. In the midst of a bitter row about GDAs vs traffic lights, why add confusion with another labelling muddle? Ashridge Business School's labelling study published last week showed only a quarter of consumers currently see climate change as important in food choice. We cannot look to labels to deliver population-wide behaviour change. Labels help the already interested make choices. We need to get the other 75% interested. Labelling cannot do that alone.

Carbon reduction is a must for the food chain. But loading it on to consumers is not the priority.