WASHINGTON — The chairman of the Federal Communications Commission on Wednesday outlined a sweeping plan to loosen the government’s oversight of high-speed internet providers, a rebuke of a landmark policy approved two years ago to ensure that all online content is treated the same by the companies that deliver broadband service to Americans.

The chairman, Ajit Pai, said high-speed internet service should no longer be treated like a public utility with strict rules, as it is now. The move would, in effect, largely leave the industry to police itself.

The plan is Mr. Pai’s most forceful action in his race to roll back rules that govern telecommunications, cable and broadcasting companies, which he says are harmful to business. But he is certain to face a contentious battle with the consumers and tech companies that rallied around the existing rules, which are meant to prevent broadband providers like AT&T and Comcast from giving special treatment to any streaming videos, news sites and other content.

“Two years ago, I warned that we were making a serious mistake,” Mr. Pai said at the Newseum in Washington, where he laid out the plan in a speech. “It’s basic economics. The more heavily you regulate something, the less of it you’re likely to get.”