National Parks across England and Wales need to "pull up their socks" to reverse the loss of wildlife from treasured landscapes, it has been urged.
National Park authorities and the Government should take steps such as tackling persecution of birds of prey and identifying areas to make "wilder" by managing land less intensively and allow nature to thrive, a report said.
Almost three quarters of important nature-rich areas known as sites of special scientific interest (SSSIs) in English National Parks are in an "unfavourable condition", the report from the Campaign for National Parks warns.
In the North York Moors, the percentage of such sites which are not in a good state is as high as 89%, while the figure is 85% in Exmoor and 84% in the Peak District.
And while National Parks are important for wildlife, with large areas designated as important international or national sites, the parks are not bucking the trend of declines in the wider countryside, the campaign group said.
Many species found in the 13 National Parks in England and Wales, from curlews to red squirrels, are struggling, though there are positive projects including boosting butterflies and supporting recovery of the pine marten.
But overall, the report says, the Westminster and Welsh Governments should work with National Park authorities to pilot a fundamentally different approach to nature conservation.
National Park authorities should show more ambition in boosting nature, including connecting up habitats, supporting reintroduction programmes and prioritising efforts to tackle persecution of birds of prey.
Government should also introduce measures to better protect birds of prey, including a system to license driven grouse shoots and make landowners liable for what happens on their land, and restore blanket peatlands and upland heaths.
Future payments to farmers and land managers should focus on protecting the environment, while it is "essential" protection for nature is maintained after the UK leaves the European Union, the campaign group urged.
Television presenter, naturalist and vice president of the Campaign for National Parks, Iolo Williams said: "The status quo isn't good enough.
"National Parks need to urgently pull their socks up and turn around the unacceptable loss of nature from the parks.
"We need landscapes that are alive with people and wildlife, buzzing with invertebrates and busy with bird life.
"Across the countryside we are facing a dire ecological decline, as special protected landscapes National Parks must set an example and lead the way forward."
Fiona Howie, chief executive of Campaign for National Parks, said: "We know there are examples of fantastic work being done in the parks to protect wildlife.
"But as vast tracts of land, and in the face of threats such as climate change, the National Parks need to be doing more for nature."
She added: "The National Parks are beautiful, well-loved and attract millions of visitors each year. But we need to see urgent change.
"We believe they could be even more beautiful and being home to thriving and flourishing wildlife is an important part of achieving that."