More than a tenth of the world's palm kernel meal, a by-product of palm oil, is fed to British pets and livestock

British cats, dogs, cows, pigs and even goldfish are helping destroy the rainforests of south-east Asia. A new study for the government finds that more than a tenth of all the world's palm kernel meal – a lucrative by-product of the production of palm oil – is fed to British animals.

Palm oil is an ingredient in an estimate third of all products on supermarket shelves, from biscuits and margarine to shampoo and confectionery. And it turns up on garage forecourts in biodiesel. Britain imports more than half a million tonnes of the oil a year. But the study for the Department of Food and Rural Affairs (Defra) reports that Britain imports even more palm kernel meal, mostly for animal feed.

The report found that while retailers and manufacturers of branded foods are rushing to buy certified "sustainable" palm oil that does not destroy the rainforests, animal feed manufacturers show "little awareness of sustainability". British imports of sustainable palm kernel meal are precisely zero.

The report, Mapping and Understanding UK Palm Oil Use, names three companies responsible for supplying most of the palm kernel meal for animal feed in Britain: the manufacturers AB Agri, owned by Associated British Foods, and BOCM Pauls, plus the commodity trader ED&F Man.

Some companies, it says, excuse themselves by claiming their product is simply a by-product of palm oil production – and oil is increasingly being certified. But the Defra official Sara Eppel, who unveiled the findings at a conference on palm oil at London zoo last Friday, said that didn't wash. "It's not just a by-product," she said, especially in Britain where "we import five times as much kernel from Indonesia as palm oil."

Eppel also reported that the British government was not blameless. It buys a lot of food and other products containing palm oil, yet "government buying standards don't currently cover palm oil sustainability". And proposed rules due this year on food purchases won't include palm oil either.

Most of the world's oil palm is grown on giant plantations in Malaysia and Indonesia, where campaigners have documented continuing deforestation to meet growing world demand. The conference heard that plantations cause an 85% loss of biodiversity. Oil comes from the oil palm's fruit, while kernel meal comes from palm nuts.

The good news from the report – compiled by Proforest, a not-for-profit consultantancy based in Britain – is that Britain is importing 40% less palm oil than five years ago. And almost a quarter of what we do import is now certified sustainable by the industry's green watchdog, the Roundtable on Sustainable Palm Oil.

The bad news is that while supermarkets and manufacturers of branded goods are responding to growing consumer concern by seeking out sustainable suppliers, others have not changed their purchasing policies. They include the nation's restaurants, canteens and pubs – and the British government.