buy only wine sealed with real cork as part of a drive to save the Iberian lynx.
The Guardian said increased demand for screwcaps and synthetic closures in the wine industry has affected the lynx habitats in the cork forests of Spain and Portugal.
It has urged readers to demand cork closures and complain to wine merchants about synthetic stoppers.
However, the World Wildlife Fund has pinpointed other factors likely to have caused a dip in population numbers, such as heavy road traffic and a decline in the rabbit population - its natural prey.
A spokesman for Oeneo, which manufactures both cork-based closures and screwcaps, said the issue was more complicated than that described by the Guardian.
"There are many other factors involved
and, as far as I know, cork forests are not actually in decline," he said.
He added: "Oeneo want s its closures to be bought as a result of their performance, not any other factor."