Drug middlemen are lashing out at Food and Drug Administration Commissioner Scott Gottlieb for saying they have a role in a practice that brand-name drug companies use to stifle competition and keep prices high.

Gottlieb spoke at CNBC’s Healthy Returns event Wednesday about a practice in which brand-name drug companies use the FDA’s safety rules to deny generic companies access to copies of their products. The comments were the latest attack from the Trump administration on the way insurers and pharmacy benefit managers, which oversee drug plans for employer-sponsored health plans, negotiate with drugmakers for rebates.