Proposals to loosen planning rules to make it easier to build houses "drives a coach and horses" through conservation efforts, a Dartmoor boss says.
The government is consulting on new legislation that could allow landowners to convert barns into houses without planning permission.
Kevin Bishop, chief executive of the Dartmoor National Park Authority (DNPA), said the move could significantly weaken the authority's conservation powers.
The BBC contacted the Department for Levelling Up, Housing and Communities for comment.
The proposals, aimed at "removing the time and money needed to submit a planning application", could also remove a requirement that shopfronts should be vacant for at least three continuous months before they are turned into homes.
The plan has been linked to government attempts to find ways to increase housebuilding in the face of a national housing shortage
But Mr Bishop said the proposals favoured development over environmental protection.
"Basically it drives a coach and horses through the powers that we have to protect Dartmoor for future generations," he said.
"On one level it's a charter for speculators and developers - it's not a charter for conservation and our communities."
High street businesses the BBC spoke to in Ashburton, on Dartmoor's southern edge, also expressed concern.
Tess Coulson, of Tess Designs, said: "We enjoy our town as it is and we don't want it spoiled by a lot of different developments."
Reuben Lenkiewicz, from Reuben Lenkiewicz Fine Art and Jewellery Gallery, said it was a "complicated issue".
He said: "Obviously people need housing, however if you lose the uniqueness of a town like Ashburton, then you lose the reason for people wanting to go there and visit."
Karen Dinnie, of Quirky Bird, said she preferred the DNPA to make local decisions "rather than somebody in Westminster".
The consultation is open until 25 September.