Labour environment spokeswoman Sue Hayman described the news as “extremely concerning”, while the RSPB said the plan seems “desperately weak”.

The leaked plan, which was signed off by Defra, comes eight months after Theresa May launched the government’s 25 year environment plan, which pledged to ensure protected areas are “not only conserved but enhanced” and introduced a new target to conserve 75% of SSSIs within the lifetime of the plan.

This plan feels like the moment of impact between aspiration and reality

Commenting on the story a spokesperson for the government’s conservation watchdog said the agency had not reduced any targets – insisting these were set by central government.

A Natural England spokesperson told Unearthed: “We are working to meet our ambition of achieving 75% favourable condition on SSSIs as part of the 25 Year environment plan. We do not comment on leaked documents.”

Protected areas

The law requires the government to “further the conservation and enhancement” of SSSIs, under the Countryside and Rights of Way Act 2000.

They protect England’s most important areas for biodiversity, from the Lake District to the Pennines to Exmoor. Unearthed has found parts of all of these areas that were recorded as being in “unfavourable” condition when they were last assessed.

Natural England ranks sites as “favourable”, “unfavourable – recovering”, “unfavourable – no change”, “unfavourable – declining”, “partially destroyed” or “destroyed”.

But a source at Natural England told Unearthed the agency could even slide backwards on its target to conserve sites.

“We don’t really know what’s happening,” the insider said. “There is very little monitoring going on and when this is combined with little to no proactive management work, there is very little hope of any gains. We could go backwards on the the target but in reality we are unlikely to know as the site condition hasn’t been checked. It is pretty shocking.”