WASHINGTON — Nearly 4 out of 5 states have not enacted laws essential to enforcing new consumer protections in President Barack Obama’s health care law, less than a year before it is supposed to be fully implemented, a new survey indicates.

Millions of Americans still stand to benefit in 2014 from protections in the Affordable Care Act, such as a new guarantee that consumers with pre-existing medical conditions cannot be denied coverage.

The law also limits how much more insurers can charge older consumers and requires health plans to cover a basic set of minimum benefits.

If the 39 states that have not enacted their own laws codifying these protections don’t do so, the federal government could step in to guarantee them. But that means Washington would essentially regulate critical parts of insurance markets that are typically state-regulated.

If state lawmakers want to retain local control, they must move this year, said Katie Keith, lead author of the survey by the New York-based Commonwealth Fund.

“We expect the 2013 legislative session to be a critical time for state policymakers who wish to limit direct federal enforcement of the reforms,” said Keith, who teaches at Georgetown University’s Center on Health Insurance Reforms.

The 11 states that have taken steps to enact these protections include many of the same ones that have moved most aggressively to implement the health care law since Obama signed it in 2010.

They are Arkansas, California, Connecticut, Maine, Maryland, New York, Oregon, Rhode Island, Utah, Vermont and Washington. The District of Columbia has also adopted the provisions.