Numerous emails appear to show close coordination between the EPA and environmental groups in drafting the controversial Clean Power Plan which could mark the demise of coal-fired power plants in the United States.

The emails, obtained by Fox News, came to light in a lawsuit filed by the Energy and Environment Legal Institute. Chris Horner, of EELI, told Fox News he believes the emails show a breach of the Administrative Procedure Act of 1946, which codifies constitutional guarantees in federal rulemaking.

"There is a process under our laws -- very specific, very precise -- detailing  how agencies are allowed to write what is, in effect, law," Horner said. "They are to afford all parties equal right to participate. They are not permitted to write rules in the backroom with your buddy or on Yahoo accounts with your buddy."

In one email, Sierra Club's lobbyist John Coequet jokes to two senior EPA executives: "Pants on Fire." That's his observation to a reference then-assistant EPA Administrator Gina McCarthy made in an Aug. 15, 2012, keynote address to Coal-Gen, a coal industry group. McCarthy told the crowd, "Coal will continue to provide more of Americans' electricity than any other fuel source, producing nearly 40 percent of all generation in 2035."

Horner said, "They all knew this was a lie. They were saying what they knew they would have to say just to get by."

In another memo, an EPA staffer writes a colleague, "Is it possible for you all to put together a summary of the arguments the Sierra Club made on why GHG [greenhouse gases] are currently regulated under the CAA [Clean Air Act]? Gina would like to get a copy."

And in another, a Sierra Club lobbyist writes how the EPA could craft a standard that no coal-fired plant could meet, while an EPA associate administrator, Michael Goo, responds on his Yahoo account, "attached is a memo I didn't want to send in public."

The power rule was finalized Monday and sets ambitious targets for cutting greenhouse gas emissions from coal-fired power plants. McCarthy, now EPA administrator, in a recent YouTube clip that lauds the open, public process behind the Clean Power Plan, said, "You know how I know we got this rule right? Because we  listened. Even before we put pen to paper on our proposal, we held hundreds of meetings and conversations. We received 4.3 million comments on our proposal."

As of publication time, EPA had not responded to requests for comment from Fox News.

The emails have prompted a congressional inquiry. Rep. Lamar Smith, R-Texas, chairman of the Committee on Science, Space and Technology, earlier wrote former assistant administrator Goo asking him to preserve all his private emails dealing with official correspondence from 2011 to 2014.  Smith wrote, "You seemingly routinely communicated with third party groups attempting to influence the Administration's agenda."

The Energy and Environment Legal Institute says it will file suit in the next 60 days to stop the Clean Power Plan. But it acknowledges the limitations of its legal recourse.

"Will EPA be allowed to impose all of the harms it intends over the few years it would take the courts to get to this, or will Congress pull the plug, or will the court issue a stay?" Horner asked.

Doug McKelway joined Fox News Channel (FNC) in November 2010 and serves as a Washington-based correspondent. Click here for more information on Doug McKelway.