Contractors have started chopping down trees on a popular dog-walking route to make way for 135 new homes.
Redrow Homes will build the controversial St Nicholas Mews housing development on land off Ballards Walk, Laindon.
The developer was given outline permission in May, with final details of the scheme being rubber stamped by Basildon Council last month.
Despite final permission only being granted in September, when planning chairman Carole Morris used delegated powers behind closed doors, fences have blocked the fields from public access since June.
Campaigners had fought to stop the development, objecting to the loss of the popular open space, but the land is not designated as green belt for planning purposes.
Residents also fear the new homes will put additional strain on existing schools and doctors’ surgeries.
Terry Latchford, 75, of Ballards Walk, said: “There are so many homes being built and we don’t have the infrastructure.
“There’s a lot of bad feeling about what is going on.”
Basildon Council sold the land to Redrow last year for £7.5million, using the money to pay off the final installment on the nearby £38million Basildon Sporting Village.
Despite the loss of park land, the approved application includes “green infrastructure”, with a public open space at the east of the site and a pedestrian link from Gloucester Park.
Some of the existing trees and shrubbery will be retained, but workers have already begun chopping down dozens of trees from the land.
A council report, written last month, said: “Garden walls and fences will be softened with small trees, shrubs and climbing plants.
“Additional planting will comprise new trees across the site and enhance the pedestrian routes and streets through the site.”
On its website, Redrow is inviting potential buyers to register their interest in the new homes, and state the development is “coming soon