Green campaigners have urged the Government not to "gamble" with England's natural heritage by allowing developers to destroy ancient woodland.
Environment Secretary Owen Paterson sparked anger after defending the "biodiversity offsetting" scheme he plans to introduce. It would allow developers to compensate for the destruction of habitats by creating or enhancing other natural areas,
Mr Paterson told The Times the policy could be applied to woods dating back more than 400 years – around a third of all woodland in England.
While destroying mature trees was a "tragic loss", replacing each with 100 new ones would "deliver a better environment over the long term", he said.
Defra said any move to build on ancient woodland would be restricted to major projects and would only get permission in exceptional cases.
Mr Paterson insisted the initiative – designed to ease the construction of homes, roads and major projects – would result in an "enormous increase" in trees.
"The point about offsetting is it will deliver a better environment over the long term," he told the newspaper.
Friends of the Earth nature campaigner Paul de Zylva said including ancient woodlands "highlights the absurdity" of the policy.
"It's the quality of forests that's important, not just the quantity of trees."
He added: "The Government's mad-cap biodiversity offsetting plans should get the chop – not our forests."
The Woodland Trust's policy director Hilary Allison told The Times offsetting should only be used as a "last resort".
The National Trust said "irreplaceable" habitats must be excluded from the policy.
A spokesman said: "Offsetting the losses of wildlife that usually accompany development by creating replacement habitats could be a useful addition to the planning system. But it mustn't mean mature irreplaceable habitats being replaced by low-quality habitats."
He added: "What Mr Paterson has said today appears to go against the Government's Green Paper on biodiversity offsetting published in September, and also raises cause for concern over protection of the green belt."
Three years ago, Mr Paterson's predecessor Caroline Spelman was forced by public outcry into a U-turn on plans to sell off England's public forests. Campaigners are now warning they could be under threat again from plans to introduce a new management organisation to "own and manage the Public Forest Estate".
Defra insists there are no plans to sell or privatise England's forests under the planned new arrangements.