An Assembly motion on the decision to allow a multimillion-pound chicken waste plant to be built near Glenavy was not debated as planned amid a fall-out between Sinn Fein and the DUP.
Sinn Fein did not go ahead with its call for Environment Minister Edwin Poots to order a public inquiry into the scheme after the DUP tabled a petition of concern.
This is a legislative method to require majority support in both communities and meant the motion was unlikely to succeed.
Angry residents opposed to the development held a demonstration at Stormont.
Communities Against Lough Neagh Incinerator (CALNI) president Danny Moore said: "The DUP's actions today mark a very low point for democracy in Northern Ireland.
"CALNI can assure (DUP) Minister Poots that using obscure legislative devices to hide from public debate on this issue will not diminish our resolve to stop him allowing this incinerator project to destroy the environment and landscape around Lough Neagh."
The campaigners include the former vice-chancellor of Queen's University, Sir George Bain. They have asked for a judicial review of the Environment Minister's decision to allow the plant to go ahead.
Mr Poots has said it represents the kind of investment needed in Northern Ireland. But residents believe he did not follow the correct planning procedures.
The group behind the incinerator proposal, Rose Energy, is a consortium of Moy Park, O'Kane Poultry and Glenfarm Holdings Limited. It says it will power 25,000 homes by burning chicken waste and bone meal.
The residents group has written to the United Nations in Geneva citing Planning Service breaches of the Aarhus Convention. The convention, agreed in 1998, guarantees the public the right to involvement in policymakers' decisions on environmental matters.