Deep in the rainforest, a squawk fills the air, discordant but strangely familiar. It is the sound of sanctimonious humbug from Europe's food industry.

For European food retailers stand accused of hypocrisy over buying palm oil from tropical countries such as Indonesia and Malaysia, where the widely used edible oil is often grown on land that once was rainforest. Many of them promised to buy sustainable palm oil if it became available.

Now, though, their bluff has been called – by the growers themselves.

For six years, many of Europe's leading food manufacturers and retailers have been members of an association called the Round Table on Sustainable Palm Oil (RSPO).

They wanted, they said, to ensure that they could buy palm oil – and the huge number of products containing it – which had been produced without destroying rainforests.

The food manufacturing giant, Unilever, started the RSPO in 2003, and dozens of food manufacturers and retailers, particularly in Europe, joined. So, less visibly, did some palm oil producers.

As demand for the oil rose for everything from margarine and shampoo to biscuits and ice-cream, the pressure grew to turn this well-meaning talking shop into a real force for change: to end forest destruction.

Ministers in Copenhagen next week will hear that deforestation is responsible for up to a fifth of CO2 emissions – and palm oil production, especially in Indonesia, is a leading incentive to tear down the remaining forests.

In response to that pressure, the food industry said it wanted very badly to use sustainable palm and would do so – just as soon as it was available. Their allies, including the environmental group WWF, which first set up the round table with Unilever, gratefully backed them. The problem, it seemed, was south-east Asian palm-oil growers.

Then just a year ago, something remarkable happened. The first boatloads of "sustainable" palm oil, certified as coming from land not recently deforested, arrived at Rotterdam. The growers were doing what their purchasers had been demanding.

But there have been very few takers. Six months ago I reported that sales were just 15,000 tonnes.

When I checked the latest stats with WWF this week, sales had risen – to somewhere between 175,000 and 250,000 tonnes. But that is a tiny fraction of what is available. Producers have the capacity to ship 1.75m tonnes of sustainable palm oil a year – getting on for 10% of total global palm oil production. But only 14% of that 1.75m tonnes was bought in the first year.

Why? "Sustainable" palm oil commands, as you would expect, a premium price. Food manufacturers know all about how to sell us green products at a premium price. But will they pay more themselves? It seems not.

And now the producers are getting wise to the reluctance of their customers to stick to their pledges. According to Adam Harrison of WWF Scotland, who sits on the RSPO board, producers are cutting production and mothballing mills that are certified for sustainable production.

This is a tragedy. Rich western corporations demand the sustainability stuff and flaunt their green credentials to customers in the process. Developing world producers, though suspicious, start producing. Rich westerners check the price tag and walk away. Meanwhile, the rainforests continue to disappear.

Who, specifically, should we blame? I asked WWF, which just produced its first "scorecard" (pdf) of sustainability for the 59 leading European retailers and manufacturers buying palm oil.

The scorecard is generous. Companies get marks just for being a member of RSPO, and for paperwork activity, like having plans to go sustainable one day.

Even so, the scores make depressing reading. Top marks would be 29. Sainsbury's and Marks & Spencer get quite close, partly through stipulating sustainable palm oil in some of their own-brand goods. They scored 26 and 25.5 respectively. Unilever, Cadbury, Asda and the Body Shop also get more than 20 marks. But even for the top scorers, "in most cases certified sustainable palm oil is still being used in only very small quantities," the WWF says.

Even on this indulgent scoring system, more than half the companies get below 10 marks. These include Waitrose, Lidl, Boots, Danone ("sustainability is part of our DNA") and Associated British Foods (makers of Kingsmill and Allinson bread).

None of these poor scorers are buying any sustainably produced palm oil, according to WWF, which has given all the listed companies a chance to correct the findings.

Waitrose's derisory 8.5 marks came as a surprise. It is part of the John Lewis Partnership, which promotes its support for the Prince's Rainforest Project, set up by the Prince of Wales to "make rainforests worth more alive than dead".

I asked them what had gone wrong. Nothing, it said. "We have committed to using only certified sustainable palm oil in our own-label products by the end of 2012. We will achieve a quarter of the conversion within the next year."

Maybe the lumbering beasts of the jungle are just slow to get moving. But, by the time they get their act together, will there be any rainforest left to protect?

This column will be watching their progress.