Tesco and M&S have admitted that their much-trumpeted initiatives to badge airfreighted fruit and vegetables have had no impact on sales.

Though they were coy about the exact figures, they said that there was no evidence yet to suggest consumers were abandoning airfreighted produce on the grounds of its higher carbon footprint.

The revelation, which came to light during the Soil Association consultation on whether to ban the use of the organic label on airfreighted produce, throws into question the label's value to consumers.

Critics said consumers either didn't understand the correlation between the label and high carbon footprints or didn't care.

However, Tesco said that the situation may have changed since the sales figures were reviewed in September and that it was still committed to developing more detailed carbon labelling for its products.

"It's still early days for the scheme," said a Tesco spokeswoman. "These findings are not in the same league as carbon labelling, where we haven't changed our thinking. Airfreighting is a very immediate, visual thing, while carbon labelling will be much more detailed, so the two can't be compared. We're still committed to establishing an industry-wide carbon labelling system with the Carbon Trust and BSI."

The two retailers started putting aeroplane logos on selected lines of airfreighted produce in April, but have since extended the scheme to cover nearly 1000 lines.

The Soil Association said it would still push ahead with its plans to develop a simple airfreight logo for licensees. Produce brought in by air would be forced to carry the badge, and suppliers would have to buy carbon offsets for the emissions, said Anna Bradley, chairman of the SA's standards board. But she admitted more work was needed to develop a workable label.

The SA is also working on full carbon labelling with the Carbon Trust.