WASHINGTON — Lois Lerner, the head of the Internal Revenue Service’s division on tax-exempt organizations, was put on administrative leave Thursday, a day after she invoked the Fifth Amendment and declined to testify before a House committee investigating her division’s targeting of conservative groups.

Lawmakers from both parties said Thursday that senior I.R.S. officials had requested Ms. Lerner’s resignation but that she refused, forcing them to put her on leave instead. Whether her suspension will lead to dismissal was unclear, given Civil Service rules that govern federal employment.

“The I.R.S. owes it to taxpayers to resolve her situation quickly,” said Senator Charles E. Grassley, Republican of Iowa. “She shouldn’t be in limbo indefinitely on the taxpayers’ dime.”

The move to put Ms. Lerner on leave came minutes after Senators Carl Levin, Democrat of Michigan, and John McCain, Republican of Arizona, released a letter to the new acting I.R.S. commissioner, Daniel I. Werfel, demanding her immediate suspension for what they said was her failure to disclose information to their Senate Permanent Subcommittee on Investigations.