There is heavy bipartisan criticism over a new proposal from the Obama administration to reduce Medicare payments for many prescription drugs.

Patients’ advocates have teamed up with doctors and pharmaceutical companies to warn the public that this proposed federal plan could jeopardize access to important medications. All members of the Senate Finance Committee — 14 Republicans and 12 Democrats — as well as more than 300 House members have expressed concerns, The New York Times reported.

In a letter to Sylvia Mathews Burwell, the secretary of health and human services, the advocacy arm of the American Cancer Society said the proposal “does not protect cancer patients’ access to the lifesaving drugs needed to treat their disease.” The plan “focuses more on the potential for cost savings” than on how to preserve and enhance the quality of care, the letter said.

Medicare’s current payment plan rewards doctors for prescribing costly drugs. In the proposal, the administration said “we intend to achieve savings.” However, it does not specify the amount it plans to save.

The first phase of the new “payment model” could begin as early as Aug. 1. The second phase, in which Medicare would base payment on a drug’s value, could begin as early as Jan. 2017.