WASHINGTON -– A top adviser to Republican presidential candidate Rep. Ron Paul (Texas) bashed fellow candidate and former Massachusetts Gov. Mitt Romney for refusing to sign an anti-abortion pledge, calling into question Romney's beliefs on the matter.

"Given Governor Romney's past flip-flops on the Right to Life issue and his support for Obamacare-like individual mandates, this stance is very troubling. Right to Life conservatives must question Gov. Romney's commitment to our cause," Jesse Benton, Paul's campaign manager, wrote in an email.

Benton was referring to Romney's decision not to sign a pledge circulated by the Susan B. Anthony List, a Washington-based anti-abortion group. Romney's campaign said Friday that the language was overbroad, would limit his ability to choose cabinet officials if he became president and would result in a loss of federal funding for hospitals--including facilities for military veterans.

Romney wrote an op-ed for National Review on Saturday further outlining and defending his decision.

But Benton wrote to HuffPost that "advocates of individual Liberty and medicine based on the free market who want to get the federal government out of our health care should be alarmed that Gov. Romney is using the very same Big Government involvement that we are fighting against to justify his soft position."

Benton's comments follow criticism of Romney on the issue by other 2012 hopefuls – former Sen. Rick Santorum (R-Pa.) and Rep. Michele Bachmann (R-Minn.) – over the weekend.

Former Godfather's Pizza CEO Herman Cain also has declined to sign the pledge. Cain said in a statement that the pledge takes too robust a view of presidential powers by calling on the president to "advance" pro-life legislation rather than Congress.

The SBA List has said Romney's concern about Cabinet appointments is a sign he wants to nominate abortion-rights advocates to top positions and has dismissed Romney's concerns about hospital funding as without grounds. Romney, SBA List President President Marjorie Dannenfelser said over the weekend, is referring to "non-existent legislation that would defund hospitals as a reason not to sign."

"Defunding hospitals has never been considered by Congress, is not part of public debate, and is not part of the pledge. 95 percent of abortions are performed outside of hospitals," Dannenfelser said.