The fiscal conservative group Americans for Tax Reform (ATR) put lawmakers on notice Monday, saying that a vote in favor of a surtax on healthcare benefits would violate any pledges they'd made to not raise taxes.

The group, which circulates anti-tax pledges for members of Congress, warned signatories of their pledge against voting in favor of a surtax to help finance healthcare reform legislation.

House Ways and Means Committee Chairman Charlie Rangel (D-N.Y.) has proposed doing such a thing, but Democratic lawmakers in the Senate have been skittish to sign onto Rangel's initiative.

(Rangel is expected to trek to the White House today to discuss his proposal.)

ATR, though, drew a line in the sand for lawmakers on the fence about the surtax, warning that the "surtax to pay for government medicine is a taxpayer protection pledge violation."

ATR was founded by conservative activist Grover Norquist.