Green activists warned the government on Saturday not to "gamble" with England's natural heritage by handing it over to profiteering developers.

Environment Secretary Owen Paterson's "biodiversity offsetting" scheme would let firms destroy habitats if they make or improve other areas.

He said that all woods older than 400 years - a third of England's woodland - could face the chop.

Mr Paterson bizarrely claimed that cutting down old trees would "deliver a better environment over the long term."

The Environment Department has drawn up limp rules which would restrict building on ancient woodland to major projects, with permission only granted in "exceptional circumstances."

Mr Paterson admitted that replacement woods could be far away and that the present generation would lose out.

But the Commons environmental audit committee said the plan was too simplistic and didn't properly account for the value of ancient woodland.

The MPs said there was a risk developers would be given "carte blanche" to rip up valuable habitats.

Friends of the Earth 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 said.

"Ministers should be protecting nature, instead of gambling with it by allowing Britain's best wildlife sites to be shifted around the country.

"The government's mad-cap biodiversity offsetting plans should get the chop - not our forests."

The Woodland Trust said more than 380 ancient woods were already under threat from projects including the HS2 high-speed rail line and that offsetting should be a "last resort."

Three years ago, Mr Paterson's predecessor Caroline Spelman was forced into an embarrassing U-turn after she planned to flog off England's forests.