WASHINGTON — Republicans plan to seek answers from Health and Human Services Secretary Kathleen Sebelius on the Obama administration’s troubled start for its health care website to buy insurance, and are raising concerns about the privacy of information that applicants submit under the new system.

GOP lawmakers said Sunday that the Obama administration will face intense scrutiny this week to be more forthcoming about how many people have actually succeeded in enrolling for coverage in the new insurance markets.

Medicare chief Marilyn Tavenner is scheduled to appear during a House hearing on Tuesday, followed Wednesday by Sebelius before the House Energy and Commerce Committee. The officials will also be grilled on how such crippling technical problems could have gone undetected prior to the Oct. 1 launch of that website, healthcare.gov.

“The incompetence in building this website is staggering,” said Rep. Marsha Blackburn, R-Tenn., second- ranking Republican on the panel and an opponent of the law.