Republicans have sought to blame President Obama for the sequester, which advocates say will significantly hamper U.S. investments in public health.
On Friday, the lawmakers said the White House's predictions of the sequester's impact — the fact it could cut hundreds of thousands of kids' vaccines, for example — were politically motivated.
"The Office of Management and Budget has not released the percentage of the across-the-board cuts required under sequestration or the methodology used by the White House to justify their 'estimates' on the 'impact of sequestration,'" the lawmakers wrote.
"Instead," they added, "the administration continues to cherry-pick sequestration examples that best suit their political needs as the president campaigns around the country instead of offering a plan."
The letter also asked for details on possible furloughs, federal employees' time spent conducting union business, and spending within HHS on travel and conferences.
The sequester hit Friday, though Obama still had not officially ordered the cuts as of 6 p.m.