World Wildlife Fund UK, the British branch of the international conservation group, has abandoned a policy of selling cards manufactured from recycled cardboard. Only one-fifth of the cards sold by the Royal Society for the Protection of Birds (RSPB) are recycled.
The charities say that they have "problems" with recycled cards, and that their supporters do not like them. But other charities, such as Christian Aid and Cafod, sell only cards made entirely from reused paper and insist that they have encountered no such difficulties.
The fund's 1999 Christmas catalogue boasts: "Every item has been measured against environmental criteria so you can be confident that when you buy from the catalogue, you will be buying products that don't cost the earth."
Last year, all its cards were printed on 100 per cent recycled paper. Now they contain only 75 per cent reused materials.
The charity says that the new paper content is made from trees grown in "sustainably managed" forests. But the fund has often said the term is meaningless: forestry firms of varying environmental standards claim to be sustainable.
The only sure way of knowing that forests are managed properly, says the fund, is when they have been certified by The Forestry Stewardship Council. None of the trees that go to make up the cards comes from forests approved under it.
The charity said the change "was not taken lightly" and that it had had "a lot of problems with the 100 per cent recycled cards". A spokesman added: "Of course we must stick to our principles, but we must deliver Christmas cards."