WASHINGTON—Conservatives on Tuesday took aim at House Speaker John Boehner's deficit-reduction proposal in the fiscal cliff talks, a dispute that was aggravated by Mr. Boehner's decision to remove some conservatives from prized committees.

Rep. Jim Jordan (R., Ohio), who heads the Republican Study Committee, an influential group of conservatives, criticized the $800 billion in new tax revenue included in Mr. Boehner's proposal to the White House. "The bad news is that it is a tax increase, and I am not going to vote for a...