Rep. Michele Bachmann (R-MN)

House Republicans launched another attack against Don Berwick, President Obama’s choice to run the Centers for Medicare & Medicaid Services.

In a letter sent to Obama Friday, 56 conservative members of the House, including Reps. Michele Bachmann (R-MN) and Steve King (R-IA), reiterated their concerns over Berwick’s work with England’s National Health Service. The letter’s signatories also derided comments Berwick made supporting comparative-effectiveness research.

“We believe that Dr. Berwick’s recommendation for the federal government to use ration-based, cost-effectiveness research to restrict patients’ access to medically-necessary care is wrong,” the letter said.

Berwick has received support from a number of medical groups, including the American Hospital Association and the National Association of Children’s Hospitals. He has also received an endorsement from the most recent CMS administrator, Mark McClellan, who recently told NPR that Berwick’s experience is “exactly the kind of background that CMS needs right now in order to find better ways to support high-quality care while saving money at the same time.”

Berwick’s official nomination hearing has not been scheduled yet.