The new King Charles Coastal Trail is said to be under threat from a major new development just weeks after its grand opening.
The move sparked anger among local residents as protesters warned the plans risked “eroding the natural character” of the area.
Protesters took a firm step against proposals to build 30 houses in a field next to the site where the British monarch, 77, inaugurated the England Coast Path at the famous Seven Sisters cliffs in East Sussex.
Lewes District Council has unveiled plans for affordable housing at Chyngton Field, a 2.7 hectare site on the outskirts of Seaford.
The proposal has sparked fierce opposition from residents, conservation groups and walkers who fear it will damage an area of outstanding natural beauty.
The field lies just behind a ridge of Cuckmere Coastguard Huts, an iconic row of buildings overlooking the Seven Sisters that has become one of the most photographed places in Britain.
King Charles chose this stretch of coast as the setting to begin the 2,700-mile coastal path, which has the distinction of being the longest in the world.
Recently, large numbers of protesters surrounded the field to express their opposition. They argued that new homes should be built on abandoned land rather than in virgin areas rich in biodiversity.
Rupert Kirby, one of those opposed to the plan, said The times: “Development of this site would erode the natural character of a nationally important landscape and set a worrying precedent for future encroachments on protected areas.
“It is not about opposing development in principle, but about putting it in the right place.”
The National Trust, Sussex Wildlife Trust and Seaford Borough Council have formally opposed the proposals.
A National Trust spokesperson said: “The natural environment is one of the district’s greatest assets. We would like the South Downs National Park environment to be conserved and protected, especially its scenic qualities, wildlife and dark skies, and we believe this applies to Chyngton Field.”
The South Downs National Park Authority has identified it as a nature-friendly action area aimed at supporting wildlife conservation efforts.
A petition demanding the council reconsider its plans has garnered more than 3,000 signatures.
A spokesperson for Lewes District Council said: “We have carried out a series of consultations across the district which gave residents the opportunity to contribute to the preparation of the local plan. Tens of thousands of people have shared their thoughts and opinions through the various consultations over the years and we are grateful to them all.”
