The federal official in charge of enforcing fair-lending laws that are intended to prevent discrimination is facing criticism for a series of racially provocative comments spanning the last 14 years.

Eric Blankenstein, head of the supervision, enforcement and fair lending division at the Consumer Financial Protection Bureau, a watchdog agency founded under President Barack Obama, apologized to agency staff members on Monday after a blog post using the N-word he wrote in 2004 as a University of Virginia law student became public.

On Wednesday, Democrats on the Senate Banking Committee asked Mick Mulvaney, the bureau’s interim director, to explain the vetting procedures used to hire Mr. Blankenstein. Mr. Mulvaney recruited Mr. Blankenstein, a close ally, from a federal trade agency post in December, shortly after being appointed to run the C.F.P.B.

“It is unclear whether his appointment is due to a failure to investigate Mr. Blankenstein’s background prior to his appointment, Mr. Blankenstein withholding information from you and the C.F.P.B., or an informed decision on your part to ignore his public comments,” wrote Senator Sherrod Brown, Democrat of Ohio and the committee’s ranking member.