Natural England has designated part of The London Resort proposed development area as a Site of Special Scientific Interest, in a move that will further complicate the development of the resort theme park.
Part of the site is home to the distinguished jumping spider, which is endangered in the and only known to live in two places in the UK.
The decision comes after a campaign by charities Buglife, RSPB and Kent Wildlife Trust to highlight the sites importance to not only the spider species but numerous other wildlife.
In response, The London Resort CEO Py Gerbeau said: "The project will of course continue", and that the decision was "just another issue to address in the long history".
The development plans for the site released at the beginning of the year ear mark part of the site as remaining a conservation area, and it is likely this portion of the plan that the development will use to demonstrate that the area remains protected.