Sainsbury's chief executive Justin King has lashed out at its rivals' green policies.
On the day the government revealed its intention to create a standard eco-label to tell consumers about the environmental impact of food, King said some retailers had created a lot of PR noise without any thought for either the consumer or the environment.
"It has been suggested that one way to help customers is by putting an air miles sticker on products," he told the NFU conference on Monday, in a reference to labelling initiatives championed by Tesco and M&S.
"I fail to see how that can be helpful. It is not always the case that air-freighted products are more environmentally damaging."
Sainsbury's would not "leap into carbon labelling" as there was no clear consensus on what could be achieved as yet, he said, adding: "When that consensus emerges we will try to lead the consumer education that is needed."
Defra secretary of state David Miliband said the government understood there needed to be an independent way of benchmarking products to help shoppers choose food with minimal environmental impact.
He said: "I want Defra to work on an open basis with producers, retailers and environmental and assurance bodies on whether we can agree on a green standard that allows consumers to know something about the environmental provenance of what they are buying."
Miliband said that he envisaged a time where environmental labelling printed alongside nutritional standards was the norm.
"This is not an easy piece of work and will take time, particularly if this includes the whole lifecycle impact of food from production to distribution."
But for the sake of the planet, he warned, the food industry had to make these changes. "If we fail to get the basics right, the difficult things will seem irrelevant."
'collaboration the answer'
News that the government is to lead efforts to create a single eco-label for the grocery market will hearten suppliers concerned at the prospect of supermarket chains attempting to go their own way.
It would be "hell on earth" if retailers did not unite behind a common standard, said Greencore group chief executive David Dilger.
"Having a common standard will be important as the measurements are ridiculously complex," he said. "But I'm certain that competitive advantage won't be developed by retailers taking individual approaches to carbon footprinting. Supermarkets are unlikely to invest time and effort into a project that won't give them a suitable competitive advantage. Collaboration is the answer here."
Gareth Stace, of Dairy UK, said: "Our members are open to carbon footprinting, but are keen to know how it is going to be done."
The Food and Drink Federation said it would get involved to help create a standard.