WASHINGTON – The U.S. Centers for Medicare and Medicaid Services named former UnitedHealth Group Inc. executive Andy Slavitt its acting administrator Friday.

The promotion continued Slavitt's fast rise through the ranks at the government agency charged with implementing expansion of health insurance coverage under the Affordable Care Act.

Slavitt replaces Marilyn Tavenner, whose tenure was tainted by the error-plagued launch of the federal health insurance exchange, HealthCare.gov.

Slavitt led the UnitedHealth subsidiary Optum that designed one of the few parts of the website that worked. The government later named Optum to lead the effort to clean up the site's frequent computer crashes and balky responses to consumers.

Slavitt succeeded in directing that repair, and in June 2014, the Centers for Medicare and Medicaid named him principal deputy administrator.

In a letter to employees Friday, Secretary of Health and Human Services Sylvia Burwell called Slavitt "a key member of the team that helped turn around the website last year."

She acknowledged the problems with the website launch that caused Tavenner to be called before committees of Congress and strongly criticized by members from both parties.

"It goes without saying that Marilyn will be remembered for her leadership in opening the health insurance marketplace," Burwell said. "It's a measure of her tenacity and dedication that after the tough initial rollout of HealthCare.gov, she helped right the ship, bringing aboard a systems integrator and overseeing an overhaul of the website."

One of the people she brought aboard was Slavitt. He came to UnitedHealth Group, the nation's largest insurer, in 2003, after UnitedHealth acquired Health Allies, which Slavitt founded and ran. Slavitt also has worked as a consultant with McKinsey & Co. and as an investment banker with Goldman Sachs.

Jim Spencer • 202-383-6123