A key drugmaker lobbying group has joined the legal fight against the federal government’s plan to negotiate Medicare drug prices.

The Pharmaceutical Research and Manufacturers of America, or PhRMA, is suing over plans laid out in the Inflation Reduction Act to give the federal coverage program more control over its pharmaceutical costs.

PhRMA said in a federal court complaint filed today that the act forces drugmakers to agree to a “government-dictated price” under the threat of a heavy tax. The complaint said Congress delegated too much authority to the U.S. Department of Health and Human Services to set prices.

It also says the program violates the due process clause of the Constitution’s Fifth Amendment “by exempting key decisions from public input and insulating them from administrative or judicial review.”

The lawsuit names HHS and its secretary, Xavier Becerra, as defendants. It also names Chiquita Brooks-LaSure, administrator of the Centers for Medicare and Medicaid Services.

An HHS spokeswoman said the department plans to “vigorously defend” the law.

The National Infusion Center Association and the Global Colon Cancer Association joined PhRMA in the complaint.

Earlier this month, the drugmakers Merck and Bristol-Myers Squibb also sued over the plan.

Medicare is the federally funded coverage program mainly for people who are age 65 and older. The Inflation Reduction Act’s plan marks the first time that the federal government will bargain directly with drug companies over the price for some of Medicare’s costliest drugs.

The government is expected to soon release rules for negotiating drug prices. It will then publish in September a list of 10 drugs that it will start price negotiations on next year.

Those prices won’t take hold until 2026.