The outgoing president of Nature Coast Marine Group is "appalled" five new fishing zones have been created in the Batemans Marine Park.
Bega MP Andrew Constance announced on December 12 recreational fishers could immediately enter the new zones before the school holidays.
"I'm just appalled and dismayed by this," Nature Coast's Bill Barker said. "There's been no consultation with the community."
Mr Barker said there was no consultation with the Marine Park Advisory Committee as the terms of previous members were up, and new members had not yet been appointed.
The five sites identified for increased access were Brou Lake (South), Clarks Bay (Freshwater Bay), Forsters Bay, Montague Island (East and South) and Nangudga Lake.
Mr Barker said winding back conservation measures in the waters around Montague Island was "just vandalism".
"Montague Island is an internationally-renowned conservation area," he said.
"I don't know what effect it will have - that is part of the problem.
"There has been no scientific study of what impact these changes will have."
He had concerns about the "procedure".
"It is legally required for there to be a two-month consultation period before any changes can be made to marine park zoning," he said.
In August, while still president of Nature Coast Marine Group and a member of the Batemans Marine Park Advisory Committee, Mr Barker wrote to Agriculture Minister Adam Marshall.
Mr Barker wanted a plan to cover issues that included zoning.
"I urge you to maintain the existing comprehensive process the government has set up to review the management of the (NSW) Marine Estate, which includes the development of a new management plan for the Batemans Marine Park," Mr Barker said.
"The Marine Estate review process has been under way for over eight years; involving legislation, organisational restructuring, extensive documentation, meetings and workshops, public consultation and preparation of submissions."
He expected consultation measures to be implemented over the "coming months" but was "dismayed" the rezoning proposal was decided by the government to be dealt with separately.
In a written response, Mr Marshall said Mr Constance had announced in February the government would fast-track consultation on the marine park sanctuary zones.
"The fast-tracked consultation on the proposed changes to sanctuary zones in the four areas and the more comprehensive review of the overall marine park are linked, however they will be run concurrently to ensure consideration of the sanctuary zone changes as soon as possible," Mr Marshall said.
"Any proposed change to sanctuary zones in those four areas would need to be subject to public consultation for a minimum of two months as required by legislation."
Mr Barker said the new fishing zones announcement "completely cuts across that process".
"What's been announced obviously doesn't involve any consultation," Mr Barker said.
"I don't think Andrew Constance cares about anyone else's opinions."
Independent Member of NSW Parliament, Justin Field, also slammed the government's announcement.
He said it was "anti-science" and "anti-environment".
"The Environment Minister, Matt Kean, has been all over the news over the last 24 hours saying that he will listen to the science - well the science is clear that marine sanctuaries are the best protection for the marine environment," Mr Field said.
"This decision will undermine the entire marine park network across the state and stall any progress in protecting our marine ecosystems."
He said NSW natural resources and the environment was not being managed properly by the Liberal Environment Minister, the "anti-science" National Party and Berejiklian Government.
"The community overwhelmingly supports marine parks and sanctuaries and they will be horrified to hear their favourite holiday spots are being undermined in this way," he said.