But the U.S. Health and Human Services Department, which includes CMS, has been pushing back in the past week against dire predictions like those of Tavenner and others about high Obamacare price hikes.
HHS pointed to similar fears that had been raised last year, when critics suggested Obamacare customers would be hit with double-digit premium increases.
Last week, HHS issued an analysis that it said "debunks the myth that average customers experienced double-digit percentage premium increases for coverage" on the Obamacare marketplace in 2011.
The analysis found that in 2016, the average premium among HealthCare.gov customer increased 8 percent from 2015 to 2016, after taking into account the shopping that existing customers did when they selected a new plan and actual new customers.
And when the federal subsidies, or tax credits, that about 85 percent of HealthCare.gov customers receive were factored in, the average net monthly price increase was only $4, or 4 percent, the analysis found.
The report said that the initial rate filings that insurers make for a coming year "do not provide sufficient information" about what customers actually will pay in that year after they enroll. The filings don't take into account the effect of customers shopping around for better deals — which two-thirds of returning customers did — or the effects of the subsidies, the report said.
And the initial filings also aren't necessarily what the final prices will look like. The report noted that under the rate-review process, states can put pressure on insurers to lower their proposed rates, or in some case can actually lower the rates themselves.