Banner-waving protesters turned out in force in a bid to save downland from the bulldozers.
A 100-strong crowd marched along the A27 at Worthing in a noisy demonstration against proposals for 90 homes on the South Downs.
Worthing Borough Council has twice refused planning permission for the development on land north of Beeches Avenue after receiving hundreds of letters of objection from residents.
But housebuilding firm Hargreaves has appealed and the matter will be decided by the Secretary of State following a public inquiry, scheduled for November.
Saturday's march was organised by the Beeches Action Group (Bag), a residents' organisation set up three years ago when the plans emerged.
Pensioners and young children held balloons and placards while chanting: "No to 90 houses. Save our downs."
Motorists on the A27 honked their support.
The demonstration began at Hill Barn Lane and finished at Beeches Avenue.
Bag chairman Karl Heryet, 41, of Pines Avenue, Worthing, said: "It's a tremendous turnout and shows the strength of feeling.
"We are talking about greenfield land in the foothills of the South Downs. It is totally the wrong site for a housing development, which seems to be more about making a profit than fulfilling a need."
Bag secretary David Barrow, 58, of Beeches Avenue, added: "The A27 is already at capacity without the added pressure of up to 200 cars feeding directly on to it on a daily basis.
"This land must be protected for the sake of future generations."
Pauline Reymond, of Pines Avenue, said: "If the Government allows this to go ahead then it is setting a dangerous precedent of building on downland.
"I fear it will all be gradually lost to development.
"The community is united on this issue and we are confident we will win the day."
They were joined on the march by Worthing's Conservative MP Tim Loughton, who said: "I fully support the residents and the council on this issue.
"There is no need for this development. Worthing is already doing its bit in terms of providing new homes.
"Only a small proportion of this development will be affordable housing.
"This Government seems determined to bulldoze our green belt.
"Building more houses like this will drive property prices up, not down. We need to look at brownfield sites first.
"The infrastructure, such as roads, schools and doctors' surgeries, cannot sustain a development of this scale."
A similar planning battle on the other side of Worthing has attracted national media attention.
Protesters trying to stop developers from cutting down part of Titnore Woods in Durrington are to appear on ITV1's Tonight With Trevor McDonald.
Weeks earlier, a group of residents were filmed burning an effigy of John Prescott in Titnore Lane, which runs past the wood.
Three construction firms have already won outline planning permission from Worthing Borough Council to create 850 homes on land next to the wood. It would involve cutting down 210 trees.
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