Two Sides, the European initiative to promote the responsible production and use of print and paper, claims that making the link between reducing the use of paper and helping the environment could contravene the Committee for Advertising Practice code.
The code states that environmental claims "must be supported by a high level of substantiation".
Research by Two Sides found that 43% of banks, 70% of telecoms companies and 30% of utilities providers are running a risk by using the environment in their marketing messages to promote lower cost electronic billing and services.
It is writing to the brands that it believes are in breach of the CAP code and has pledged to lodge a complaint with the Advertising Standards Authority if the concerns are not addressed.
Martyn Eustace, Two Sides director, said: "If organisations want to encourage customers to switch to e-billing because they believe it offers efficiency, then we have no quarrel with that, but we will fight all the way to stop them from making a link between reducing the use of paper and helping the environment – unless they have proof that this is so."