Washington (CNN) -- A controversial bill that would have stopped the Environmental Protection Agency from regulating carbon emissions was defeated in the Senate on Thursday, falling four votes shy of the 51 needed for passage.
Six Democrats joined a unified Republican caucus in backing the measure.
The "resolution of disapproval" proposed by Alaska GOP Sen. Lisa Murkowski would have prevented the EPA from further regulating air pollution from vehicles and industrial facilities. Murkowski argued that new rules should be created only by Congress, not an executive agency.
"It would amount to an unprecedented power grab, ceding Congress' responsibilities to unelected bureaucrats and move a very, very important debate, a critical debate, from our open halls to behind an agency's closed doors," Murkowski said shortly before the vote on the Senate floor.
The plan was vehemently opposed by environmentalists, who say that the EPA's decision to regulate greenhouse gases is based on scientific research and that putting the regulation in the hands of Congress would subject it to political maneuverings.
"I believe it's ridiculous for politicians, elected senators, to make this scientific decision. It is not our expertise," said Sen. Barbara Boxer, D-California, chairwoman of the Senate Environment and Public Works Committee. "We've got to stop this attack on science and health."
Even if the measure had passed the Senate, its prospects in the House were considered slim. Regardless, the White House on Tuesday issued a veto threat if it made it to President Barack Obama's desk.
The Murkowski resolution "would undermine the administration's efforts to reduce the negative impacts of pollution and the risks associated with environmental catastrophes, like the ongoing BP oil spill," said a White House policy statement.
At issue was a Supreme Court ruling from 2007, which determined that the EPA has the authority to regulate greenhouse gases under the rules of the Clean Air Act. In December, the EPA concluded scientific findings and declared that carbon dioxide and five other gases constitute pollutants that should be further restricted. And the agency announced in April new rules for vehicles: a mandatory increase in fuel efficiency coupled with reductions in gas emissions, starting with 2012 model years.
Lisa Jackson, the EPA administrator, wrote a column Monday in the Huffington Post accusing Murkowski of siding with "big oil companies and their lobbyists" in an effort to "take away EPA's ability to protect the health and welfare of Americans from greenhouse gas pollution."
Supporters of Murkowski's resolution said the Clean Air Act was never intended to give federal agencies full control over greenhouse regulations but rather to check industrial and commercial structures. Such regulatory decisions, they argued, should be made by Congress.
"I think the EPA needs to understand it's not the fourth branch of government," Sen. Ben Nelson, D-Nebraska, who supports the limits on EPA, said Tuesday. "Just because they are dissatisfied with the level of progress of the legislative branch doesn't empower them to become super-legislators."
Murkowski said she was leading this effort not because she is a skeptic of global warming but because she wants Congress to be proactive on new environmental policies.
"We are not going after the science. That was not my intention," she said.
Senate Majority Leader Harry Reid has said he wants the Senate to approve new energy legislation this summer to address both global warming and the oil spill in the Gulf of Mexico.