The WWF has slammed food retailers and manufacturers for failing to support growers of sustainable palm oil.

Grocers had produced 1.3 million tonnes of certified sustainable palm oil, but only sold 15,000 tonnes - just 1% of the total produced - according to the conservation charity.

The "sluggish performance" threatened rainforests and could lead to growers withdrawing from sustainable schemes, it warned, calling on companies that use the oil to commit to using only sustainable oil by 2015, and to begin purchasing it immediately to support growers already signed up to the scheme.

However, the WWF praised suppliers such as Unilever that have signed up to a round table on sustainable oil, and Sainsbury's, which has committed to using only sustainable palm oil by 2014. "We applaud the leadership of companies like Sainsbury's, which have backed up their public commitment with action," said Adam Harrison, senior policy officer for food and agriculture.

Conventionally produced palm oil is widely used in ready meals and frozen foods as a low-cost alternative to other vegetable oils, but has been linked with the destruction of South American rainforests.