The firm left the 95+ Group, the WWF's responsible timber trade group, after a row over the tagline of Tetra Pak's 4m television and print drive.

The campaign runs with the slogan: "Because the trees we use are replaced by even more trees, when you choose cartons you're helping to grow more forests."

WWF has branded that claim "misleading". "We have a problem with that kind of language," said Sue Windebank, a spokesman for the charity. "It's not good for consumers to imply that, just because you replant a tree somewhere for every tree that's cut down, it's good for the environment."

Tetra Pak sources around 30% of its timber from woodland with Forest Stewardship Council (FSC) certification the only standard seen as economically, environmentally and socially sound by the WWF.

A level of 30% would allow Tetra Pak to use the FSC label on its packaging. But Windebank said until that paper is actually in the cartons, the company cannot claim its papers are environmentally sound.

"Rather than wait six months and get enough certified paper into their cartons, they felt they had to go ahead with this campaign now before they could make a credible environmental claim," said Windebank.

Richard Hands, Tetra Pak's environment manager, said its sources were acceptable. "Our other timber comes from equally well run and managed forests. It's just that they don't belong to the FSC scheme," he told the Daily Telegraph last week.

He added: "So many countries have different schemes. Finland, where we buy from, has its own scheme and then there is the Pan European Forest Certification Scheme, which covers other forests."

News of Tetra Pak's resignation follows recent calls from the paper industry for a single certification scheme (PrintWeek, 1 April). The 95+ Group was recently relaunched as the WWF Forest and Trade Network.

Story by Josh Brooks