A Canadian pipeline company will no longer work with a controversial U.S. public relations firm on the Energy East proposal after leaked documents raised concerns about suggested tactics.

TransCanada has cut ties with the multinational firm Edelman on the campaign to build support for a plan to bring Alberta's oilsands crude to eastern refineries after it recommended secretly using third parties to attack the pipeline's opponents.

The tactics were contained in documents leaked to the environmental group Greenpeace.

"In the current environment, we can't have the respectful conversation that we want to have with Canadians and Quebecers about Energy East," TransCanada spokesman Tim Duboyce said Wednesday in a release.

"We need to discuss the project on its merits, responding to valid concerns such as how we will protect water and marine life, instead of talking about communications tactics."

The documents outlined what Edelman call a strategy with a "strong heritage in the more aggressive politics and policy fights in the U.S."

Edelman recommended working with proxies to secretly "add layers of difficulties for our opponents," the documents say. The plan suggested TransCanada conduct research on environmental groups and hand the results over to third parties, who can "put the pressure on, especially when TransCanada can't.

"We will work with third parties and arm them with the information they need to pressure opponents and distract them from their mission."

TransCanada immediately denied it had implemented those tactics, which were widely criticized.

Edelman defended its proposal in a statement released Wednesday, the first time it had addressed the issue.

"We stand by our strategy," it said. "It was both ethical and moral, and any suggestion to the contrary is untrue.

"Unfortunately, the conversation about our efforts has become so loud in certain areas that it is impossible to have an open and honest conversation about the pipeline project."

TransCanada has its work cut out for it, said Keith Stewart of Greenpeace.

"They're going to face a skeptical public," he said.

"We want to see a different approach, not just a different PR company. How the debate is conducted is always important to the substance of the debate."

TransCanada has acknowledged some of Edelman's advice is in play. The company will collect publicly available information on its opponents and has started an extensive social media campaign.

But spokesman James Millar said TransCanada will also increase its community meetings and public engagement.

"You need to get out there and speak to people," he said. "That's a good idea on both sides."

Millar said TransCanada signed up 1,500 supporters on its social media website last week after news broke about Edelman's suggestions.

"It's not the old world that a lot of people are used to. There's a new way of doing business and that means engaging with people on their own turf and on their own terms and we need to focus on that."