The forest carbon offsets approved by the world’s leading provider and used by Disney, Shell, Gucci and other big corporations are largely worthless and could make global heating worse, according to a new investigation.

The research into Verra, the world’s leading carbon standard for the rapidly growing $2bn (£1.6bn) voluntary offsets market, has found that, based on analysis of a significant percentage of the projects, more than 90% of their rainforest offset credits – among the most commonly used by companies – are likely to be “phantom credits” and do not represent genuine carbon reductions.

The analysis raises questions over the credits bought by a number of internationally renowned companies – some of them have labelled their products “carbon neutral”, or have told their consumers they can fly, buy new clothes or eat certain foods without making the climate crisis worse.

But doubts have been raised repeatedly over whether they are really effective.