(CNN) - South Carolina Sen. Jim DeMint is out with a fundraising pitch that goes after his party for conducting "business as usual."
DeMint is blasting Republicans who, in a closed-door meeting on Wednesday, voted to allow Alaska Sen. Lisa Murkowski to retain her leadership position on the Senate Energy and Natural Resources Committee.
"It was bad enough to watch my colleagues work to support [Murkowski] in the primary after she had built a record of betraying conservatives principles," DeMint wrote Saturday in an e-mail to supporters of his PAC, Senate Conservatives Fund. "But watching them back her after she left the party and launched a campaign against the Republican nominee was more than I could bear."
DeMint has clashed with his party establishment's leaders this election cycle, as he's backed staunchly conservative candidates over the sometimes more moderate GOP-backed ones.
Murkowski lost to attorney Joe Miller last month in her state's primary. Miller had DeMint's backing as well as that of the Tea Party movement. Earlier this month, Murkowski announced she would mount a write-in bid to retain her Senate seat. Sarah Palin and the Tea Party Express group condemned the move, and the Republican Party establishment said it would stand by Miller as the party's nominee.
The decision not to remove Murkowski from the top position surprised many in the political world given that the GOP has now backed her opponent.
A GOP source in Wednesday's meeting told CNN that despite anger towards Murkowski, the conference decided not to even take up the question of the Senate Energy Committee post because "there was a sense that she's resigned her leadership post, she lost her primary, she will probably lose her race, and she'll be gone. She will not be ranking [Republican] because she will not be here."
In his fundraising appeal, DeMint accused his party establishment of hypocrisy.
"I was attacked just last week by the Washington establishment for supporting Christine O'Donnell – a conservative – because they believe her nomination will hand the seat to a Democrat in Delaware," DeMint wrote. "This week, however, that same establishment voted to help Lisa Murkowski – a moderate – defeat the Republican nominee, which could hand the seat to a Democrat in Alaska."
"The Washington establishment is doing everything it can to help Lisa Murkowski hold on to power. The grassroots defeated her once in the primary election and we can do it again in November," he added.
–CNN's Dana Bash and Ted Barrett contributed to this report