The group says it will be a death knell for the area's birdlife, including critically endangered Eastern Curlews and Beach Stone-curlews.

A community-led push is underway to see a safe and navigable waterway to the entrance of the Manning River at Harrington and a permanently open entrance at Farquhar Inlet.

Leading the campaign is the Manning River Action Group, who are calling on MidCoast councillors to lobby the Member for Myall Lakes Stephen Bromhead and Federal Member for Lyne Dr David Gillespie MP to assist with secure funding for the project.

Support has come from a number of areas, including the fishing industry, oyster farmers, dairy farmers, Harrington Chamber, Business Taree, Team Taree, Businessmen's Association, recreational fishers, tourism operators and moteliers, building industry, legal fraternity, sporting clubs, real estate industry and the indigenous community.

The action groups says managed areas for protection of shorebirds, including Little Terns, is now urgent; flood mitigation is high on the agenda as is protecting Manning Point from serious flood damage; and clean water for the oyster farmers and fishing industries is paramount.

Mr Bromhead said a ministerial taskforce has reviewed options for providing a permanent entrance to the Manning River and a report will be presented to the government.

BirdLife Australia condemns the proposal, which could permanently destroy vital habitat for migratory shorebirds, seabirds and beach-nesting birds, and is asking the NSW government, which is funding the strategic business case for the plan, take into account the significant environmental and economic concerns of the local community.

Hastings Birdwatchers representative Peter West said the proposal would result in permanent habitat damage.

"I'm really concerned about the possible changes proposed for the Manning estuary at Farquhar Inlet, Old Bar, and at Harrington," Mr West said.

"Both sites are wonderful natural places as shown by the large numbers of migratory and local shorebirds using the estuary.

"Many of these are threatened, such as the critically endangered Eastern Curlew, and so protected by the EPBC Act.

"The mudflats are key feeding areas and the sand dunes are nesting sites for several endangered species including the Little Tern and Australian Pied Oystercatcher. A pair of critically endangered Beach Stone-curlews also breed there.

"With many years of surveying the birds at these sites we know the damage that could be done by dredging and construction of break walls."

BirdLife Australia's Mick Roderick said in summer, this area is home to migratory birds that fly halfway across the world to feed and rest on the spits and sandbars.

"Dredging them up and building a wall will mean they have nowhere to go," Mr Roderick said.

"Many of these birds are already threatened with imminent extinction. This move will only hasten the demise of these magnificent creatures.

"Whatever way you spin it, this is a terrible idea. It just doesn't add up, economically or environmentally."

The Manning River Estuary is recognised as a nationally significant area for Pacific Golden Plovers, Double-banded Plovers, Sanderlings and Eastern Curlews. It is also one of the most important Little Tern breeding sites in NSW and home to a pair of breeding Beach Stone-curlews, which are critically endangered in the state.

BirdLife Australia's head of conservation, Samantha Vine, said nature laws need to be strengthened so nationally important habitat for endangered species remain protected.

Ms Vine said the area is the only place in Australia to see Aleutian Terns, Kentish Plovers and other vagrant birds, and visitors regularly flock to catch sight of these elusive visitors.

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