The proposed South Downs national park has been dubbed a Jurassic Park which would lead to a fossilised environment.
Sussex Enterprise says businesses on the South Coast could find themselves squashed without room to expand.
Head of policy Mark Froud said businesses backed the park in principle but the boundaries were too far-reaching and the structure for running the park should change.
He said: "There is a danger the current plans from the Countryside Agency will fossilise the area and we will end up with a Jurassic Park.
"Businesses would like to see a modern national park that benefits the people who live and work here.
"If businesses are not allowed to expand, we will be throwing away opportunities for jobs and economic growth."
He said the proposed boundaries should be redrawn to allow room for expansion and businesses should be represented on the park authority.
The Countryside Agency is consulting on the park until February 28.
It expects to publish a designation order later this year, which will almost certainly be subject to a public inquiry before the park is created.
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