Vast swathes of green spaces in one of south London's biggest parks will be "bulldozed" if an open-air music venue is created, campaigners have said.
Burgess Park in Peckham received £6m for a revamp and in November LDA Design won the bid to transform the park.
Burgess Park Action Group said play area for children and trees would go if an amphitheatre space was built.
But Southwark Council said it planned to "reshape grassy areas" to provide a better view for events at the park.
The park, which lies between Camberwell, Walworth and Peckham, received £2m from the mayor's Priority Parks scheme and £4m from the New Deal for Communities.
'Trashing our park'
The council said the money would fund the first phase of the redevelopment by 2012, which includes creating an open-air space to accommodate 100,000 people, pathways and lakes.
But Burgess Park Action Group opposes the plans and claims that 70% of the park is at risk.
A playground, cycle path, a woodland area and wildflower meadows are some of the things that could be lost, the group said.
Donnachadh McCarthy, from the group, said: "This is our countryside so actually to trash it and put in a venue for 100,000 people and bulldoze footpaths straight to the amphitheatre through the park is trashing.
"This is our fresh air."
But Southwark Council said the project would create "more adventurous activities" in a derelict play area and involve the planting of 2,000 new trees.
Councillor Barrie Hargrove, cabinet member for environment, explained that the open-air venue would not be a stadium-like construction.
"There are no plans to build a physical amphitheatre in the park.
"In the document that's currently out for consultation there are proposals to create a better view of the space where events like the annual Latin American Festival Carnaval Del Pueblo currently take place in the middle of the park."
The plan is currently open to a public consultation.