A report commissioned by the UK government on how to improve environmental labelling on food products has outlined the difficulties of producing a single "green" label.

The report by the University of Hertfordshire, the Food Ethics Council and the Policy Studies Institute today (7 February) revealed that the number of different environmental labels on food - covering issues such as carbon emissions and water use - has been growing. The number of labels, the report noted, has "raised concerns that consumers may be confused or misled", generating interest in developing an 'omni-label' - a single environmental label that covers all the main environmental issues.

The research examined whether the development of an 'omni-label' would be possible, exploring the strengths and weakness of the science behind labelling. It reviewed 70 existing labelling schemes, and considered the practicalities of labelling for consumers and businesses.

One key finding from the report was that most existing environmental labels tell consumers how their food was produced but do not measure the direct environmental impact of individual products.

These "practice-based" labels, the report acknowledged, can play "a valuable role in engaging shoppers with environmental issues", and are likely to remain "more cost effective than "outcome-based omni-labels".

However, the report said that, at present, the science is "not robust enough" to develop a broad omni-label that accurately tells consumers the environmental impacts of specific food products.

Measuring the impact on the environment is crucial to helping businesses become greener, but there remain "big technical challenges", the report said. It added that efforts to reduce the environmental impacts of food should not focus primarily on labelling.

Dr Tom MacMillan, executive director of the Food Ethics Council, said: "This research is the largest review to date of environmental labelling on food products, and offers a set of priorities that should help make labelling clearer and more effective.

"But it's also a wake-up call to anyone who thinks labelling alone will save the planet, as many of the technical and practical challenges we found won't go away soon. It's a fact of life that simplifying different environmental impacts clearly in one label is tricky, and shoppers will always have plenty else on their mind when they're buying food."