Three conservation groups have asked a federal judge to halt Central Maine Power parent company Avangrid’s plans to begin construction in early December on a hydroelectric power transmission line through western Maine.

The Appalachian Mountain Club, Natural Resources Council of Maine and Sierra Club Maine filed a motion for a preliminary injunction Wednesday to prevent work starting on the corridor project until the court can fully consider a lawsuit filed by the three groups challenging the U.S. Army Corps of Engineers for what they allege was a flawed and inadequate environmental review of the project.

“It is not in the best interests of Maine people for CMP to start work prematurely on what is one of the most consequential and controversial projects in recent history,” the groups said Thursday in a statement. “The federal review of this project has been conducted behind closed doors and has failed to properly consider the long-lasting impact the transmission line will have on the woods, waters, wildlife and recreational economy of western Maine.”

Thorn Dickinson, president and CEO of project developer NECEC LLC Transmission, said the legal maneuver is merely another attempt by opponents aligned with out-of-state fossil fuel companies to delay a project that all regulators agree is good for Maine’s environment and economy.

“Every final regulatory and court decision to date has approved the project and rejected every challenge,” Dickinson said in a statement. “We expect the same from the remaining approvals because the project provides substantial public benefits and has been designed to meet and exceed the most stringent environmental requirements. We continue to move forward with the project and are preparing to start construction in early December now that we have the U.S. Army Corp of Engineers permit, which was the result of an extensive and thorough review by federal officials in coordination with Maine regulators.”

Avangrid announced last week that the Army Corps had granted its approval for the project, known as the New England Clean Energy Connect. Issuance of a presidential permit that would allow the transmission line to cross the Canadian border is the only significant regulatory permit left to obtain, it said. The U.S. Department of Energy issues presidential permits.

The project to build a 145-mile-long transmission corridor that would cut through about 53 miles of undeveloped forestland in western Maine already has received permits from the Maine Public Utilities Commission, the Maine Land Use Planning Commission and the Maine Department of Environmental Protection. It would deliver hydroelectric power from Canadian utility Hydro-Quebec to the New England grid through a $ 1 billion project funded by Massachusetts ratepayers.

Since the project was proposed, there has been ongoing opposition from Maine residents, towns and environmental groups concerned about the negative impact they believe the project could have on the environment.

The Army Corps conducted an environmental review of the project’s impact and published a report in July that was not made public until the Natural Resources Council obtained a copy through a Freedom of Information Act request. In its report, the Army Corps concluded that the transmission line would have no significant environmental impact.

But last month, the Appalachian Mountain Club, Natural Resources Council and Sierra Club filed a lawsuit in U.S. District Court claiming the Army Corps failed to rigorously assess the transmission corridor project’s environmental impact. The case is still pending.