Campaigners including the US author Bill Bryson have renewed their fight to save countryside across Sussex.
They were speaking after the Government announced it would take another look at plans to cut the size of the South Downs National Park by a quarter.
Since the announcement campaigners have been busy preparing their argument for the inclusion of the "western Weald"
when the public inquiry into the park reopens in February.
Mr Bryson, who is president of the Campaign to Protect Rural England (CPRE), visited the area in September.
He said he was "shocked" to see the planning inspector's argument to exclude a large tract of land known as the western Weald from the national park because it is a different type of landscape from the chalk downland. He said: "This countryside is some of England's finest and one of the glories of the English landscape is its huge variety.
"If this beautiful landscape is left out of the national park, it will run the risk of being picked off by developers and lost forever."
The Department for the Environment, Food and Rural Affairs (Defra) announced last Thursday it was to reopen the public inquiry after pressure from the public and groups such as the CPRE.
Since then the South Downs Campaign group has been busy planning for the preinquiry meeting at Hove Town Hall on December 11 and the inquiry on February 12 next year.
It is urging people who responded to the public consultation to return forms they have been sent from Defra.
Robin Crane, chairman of the campaign, said: "It is very important that people fill in the form and get it back to the planning inspectorate by November 8, otherwise there is a risk they will lose their right to speak at the inquiry.
"Unfortunately, the form Defra has issued is far from helpful as it does not address the minister's request that the inspector considers all the issues raised during the public consultation.
"If people can't speak on these issues then the inspector is hardly going to be in a position to decide whether to change any of his recommendations.
"Given the uncertainty around subjects to be discussed at the inquiry, we are urging everyone to attend the preinquiry meeting to demand their right to be heard."
The original plan for the park was drawn up in 2002 but the process was halted in 2005 due to a legal challenge over the borders of the New Forest National Park, which could have had implications for the Downs.
It was restarted this summer but with different boundaries, cutting out 23 per cent of the area of the 2002 plans. This prompted calls from campaigners, led by Bryson, for the rethink.
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