ConocoPhillips, BP America Quit Climate Coalition
They said they backed efforts for a green economy but felt that proposed laws were unfair to them.
The firms will not renew membership in USCAP.
ConocoPhillips and BP America, a unit of British giant BP, said the bill under consideration did not attach enough importance to natural gas, which they promote as a way to curb carbon emissions blamed for global warming.
The bills "have disadvantaged the transportation sector and its consumers, left domestic refineries unfairly penalized versus international competition, and ignored the critical role that natural gas can play in reducing greenhouse gas emissions," said Jim Mulva, ConocoPhilips CEO.
In a statement, USCAP said its membership periodically changed and that it expected more companies to join.
Companies that remain in USCAP include oil giant Shell, conglomerates General Electric and Honeywell, as well as Ford and General Motors.
Edited by Ellie Duncan