Campaigner Tony North said plans to build 600 new homes on land known as the Seven Cornfields between Sedgley and Penn would have a devastating effect on the local environment.
"We will continue our fight to insist that not a brick is laid on that site," he said.
He has been backed by Wolverhampton South West MP Stuart Anderson, and Dudley North MP Marco Longhi who have both pledged to fight the proposals.
"No way should one single house be built on that land," said Mr Anderson.
"I will do everything I can to stop this plan."
It was revealed last week that Barratt Homes had drawn up proposals to develop fields between the Park Hall Hotel and Colton Hills School, prompting one councillor to threaten his resignation if the scheme went ahead.
More than 7,000 residents have signed a petition objecting to any proposed development on the 284-acre site which straddles Wolverhampton and South Staffordshire councils.
The adjoining Alder Coppice, a designated ancient woodland which comes under Dudley Council, is not part of the proposals, and is a protected local nature reserve.
Barratt and David Wilson homes wanted to build a total of 1,300 homes in the area, but the proposals received a setback after South Staffordshire Council declined to include the site on its list of locations suitable for housing.
Barratt has now come up with a scaled down 'Wolverhampton only' scheme.
Councillor Paul Birch, whose Blakenhall ward covers the site, said he would resign from the council if it went ahead.
Mr North, who lives in Northway, Sedgley, said the site was totally unsuitable and that the plans would be fiercely resisted.
He said there were plenty of brownfield sites more than capable of meeting local housing requirements.
Mr North added that the real need was for affordable housing in the area, and it was highly unlikely the scheme being proposed would make a meaningful contribution to that.
He said the site was classed as a 'high harm' location, meaning that it could only be built on if the developer could prove exceptional circumstances.
"The land forms a green wedge between Dudley and Wolverhampton; it's a wildlife corridor which stretches from the Shropshire border, through Wombourne, up to Penn Common, and then on to Sedgley Beacon," said Mr North.
"It's a very diverse ecosystem which allows both plants and animals to move along it. The impact it will have on the environment will be enormous."
Mr North said as well as the environmental damage, a development on this scale would place a huge strain on public services.
"That will be an extra 1,800 people who will need a doctor, who will need access to a hospital, the schools are already overcrowded," he said.
"The people who live in these houses will also have motor cars, and roads in the area already heavily congested, Goldthorn Hill is somewhere you will avoid if you can.
"And if cars are stuck in traffic they will produce a lot of carbon monoxide."
Mr North added that the area featured a lot of public footpaths, which had become extremely important to people during the lockdown.
Dudley North MP Marco Longhi, whose constituency borders the site, said the scheme would 'destroy' the green belt.
“This would create settlement coalescence and would directly encroach on the countryside," he said.
"In addition, this type of development would not assist the urban regeneration plan for the West Midlands Combined authority."
Mr Longhi said future housing needs should be met by brownfield development.
“We must focus on brownfield sites that blight our area," he added.
"Big investments into town centres, including housing is the future for regeneration not stripping our precious green belt.
“Any request to destroy the green belt must be rejected by local councils to ensure they are following the National Planning Framework, as well as adhering to the urban regeneration plan.
“I will work alongside residents to protect the green belt for future generations, especially with residents in Gornal and Sedgley who live adjacent to our green belt.”