Speaking at the Garden Centre Association (GCA) conference in Henley-on-Arden this week, Porritt said centres that say they are green but do not have environmental policies, such as the Garden Centre Group (GCG), are making "preposterous" claims.
The GCG dropped its "Plan Apple" policy in 2008. A show of hands at the conference demonstrated that only a couple of the 42 garden centres represented had an "essential" environmental policy.
Former Friends of the Earth director Porritt added: "I don't understand that. Garden centres are more under the spotlight than ordinary companies. It's a disappointment that they are not taking a leadership role."
The Eden Project's Dr Tony Kendle said garden centres need to focus on "the interface between gardeners and nature" rather than just selling "stuff".
He added: "garden centres need to be a place of experience, not a place of buying bits. We have to kill the poisonous word 'consumer' because gardeners don't consume all that we're talking about — they are explorers, adventurers and growers."
Government agency Envirowise representative Simon Drury accepted that businesses used to associate environmental improvements with higher costs but insisted that attitudes are changing.
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