PORTLAND — Environmental groups took aim Monday at a proposal to build a privately funded toll highway across the midsection of Maine, claiming the road would pose a threat to the state’s environment and tourism economy.

A 220-mile highway creating a direct link from Calais, on the New Brunswick border in eastern Maine, to Coburn Gore along the Quebec border in the west, would cross or come close to more than 60 significant conservation and recreation areas, the heads of the Forest Ecology Network and Restore: The North Woods said at a news conference.

They maintained that a four-lane highway would hurt Maine’s tourism economy and generate few jobs and economic benefits. They said the highway’s right of way could also serve as a corridor for oil and natural gas pipelines and large electrical transmission lines.

“It’s a colossal threat to Maine’s environment and economy,” said Jonathan Carter, director of the Forest Ecology Network.

Peter Vigue, who is spearheading the proposal as CEO and chairman of the Pittsfield-based Cianbro Corp. construction company, said any environmental impacts would be minimized and that the road would provide an economic boost to Maine, particularly in the state’s sparsely populated areas where incomes are low and jobs are scarce. There are no plans in the works for pipelines or transmission lines on the 500-foot-wide corridor, he said.

Carter and Jym St. Pierre, director of Restore: The North Woods, are known for their opposition to development, he said.

“These people have no plan for the economy and the future of the state other than to lock it and block it, lock it up and block it from future development,” Vigue said in a telephone interview while traveling.

The idea of an east-west highway across Maine has been debated since the 1960s.

It’s apparent that the federal and state governments can’t afford to build such a highway, Vigue said, so he’s proposing to build a toll road at a cost of $2 billion, which has been billed as the biggest private development ever in Maine.

The Maine Legislature this year appropriated $300,000 for a feasibility study. If the project proceeds, it would be paid for by private investors.

Carter and St. Pierre actively opposed Plum Creek Timber Co.’s proposal for a sprawling resort and residential development in the Moosehead Lake region at the gateway to Maine’s North Woods. That proposal has been approved, but construction has not started.

St. Pierre said Monday it’s time for Mainers to begin asking questions about the proposed highway’s environmental impacts, economic costs and benefits, and whether property would be taken by eminent domain.

A precise map of the highway route has not been released, but St. Pierre created a map of what he said was a likely route based on previous studies and Vigue’s public presentations.

St. Pierre’s map shows where the highway would cross or come close to wildlife refuges, rivers, streams, forests, snowmobile trails and the Appalachian Trail.

“By making Maine just one more drive-thru state, the east-west highway and corridor could destroy some of Maine’s best natural assets and put the state at a competitive disadvantage,” he said.

The feasibility study is due to be released in January.

If the project moves forward, planning and design of the highway could begin next year, with construction beginning in 2016 and vehicles rolling in 2019, Vigue said.