Department of Health & Human Services  Secretary Kathleen Sebelius testifies before a House Education and the Workforce Committee hearing on Capitol Hill in June  2013. (Jim Bourg/Reuters)

Secretary of Health and Human Services Kathleen Sebelius says in a new op-ed that a House oversight committee hearing in Texas on Monday is "designed to stifle, intimidate and impugn the reputation" of Obamacare navigators.

The hearing, which is being run by committee Chairman Darrel Issa (R-Calif.), will be held in Dallas and is titled, "Who are the navigators?" Navigators are people who help others sign up for Obamacare.

"What opponents of the new law could not do legislatively, at the ballot box, or even by shutting down the federal government, they’re now trying to do through other means," Sebelius says in the op-ed  in the Dallas Morning News. "Case in point is Monday’s congressional hearing in Dallas, designed to stifle, intimidate and impugn the reputation of people who have been working hard to help their fellow Texans get covered.

In a dueling op-ed, Issa and Dallas-area Rep. Pete Sessions (R-Tex.) cite "numerous examples of fraudulent activity related to health navigators in Texas."

Issa and Sessions argue that the navigator program lacks sufficient guidelines — including by allowing non-government employees to ask people for confidential financial information and allowing convicted felons to serve as navigators.

"Even as U.S. Department of Health and Human Services Secretary Kathleen Sebelius admitted before Congress that the lack of federal requirements raises a 'possible' problem, the administration has continued to call common-sense safeguards 'cumbersome,' " Issa and Sessions write.

Democrats have contended that GOP questions about navigators are designed to impede the law by discouraging people from serving as navigators.

The hearing in Dallas begins at 2:30 p.m. Eastern time.