The Justice Department responded Friday to Sen. David Vitter’s request for more information about its enforcement of a federal voter registration law — a response the Louisiana Republican demanded before deciding whether to drop his threat to block the nomination of Thomas Perez as the next Labor secretary.

Judith C. Appelbaum, the DOJ’s principal deputy assistant attorney general, sent Vitter a two-page letter addressing his contention that the department — specifically the Civil Rights Division now headed by Perez — has practiced “selective enforcement” of the National Voter Registration Act. The 1993 statute (PL 103-31) is intended to streamline the voter registration process in the states.

In her response, Appelbaum referred Vitter to a March 12 report by the Justice Department’s inspector general, Michael E. Horowitz, that she said refutes those allegations.

“The department’s Office of the Inspector General investigated a number of allegations regarding the department’s NVRA enforcement and concluded, in a report issued last week, that the Department of Justice in this administration has not enforced the NVRA in a discriminatory or partisan manner,” Appelbaum wrote.

Vitter’s office did not immediately respond to inquiries Friday about whether he would drop his threat to block Perez’s nomination as a result of the DOJ letter. Vitter spokesman Luke Bolar said in a Wednesday interview that he was hopeful the situation could be resolved without a filibuster.

“I don’t know if it would get to that point or not,” Bolar said.

Since 2011, Vitter has accused the department of aggressively enforcing Section 7 of the National Voter Registration Act, which requires certain government offices, such as state welfare agencies, to provide voter registration forms. At the same time, he has argued that the department has placed far less emphasis on another section of the law, Section 8, which requires states to ensure that ineligible voters such as felons, illegal immigrants and the deceased are scrubbed from voter rolls.

Vitter said Monday — two hours after President Barack Obama nominated Perez to lead the Labor Department — that he would block the nomination until the Justice Department responded to his claims of selective enforcement of the voter registration law.

“Perez was greatly involved in the DOJ’s partisan full-court press to pressure Louisiana’s secretary of state to only enforce one side of the law — the side that specifically benefits the politics of the president and his administration at the expense of identity security of each and every Louisianian on the voter rolls,” Vitter said in a statement.

Appelbaum declined to respond to Vitter’s specific comments about Louisiana, noting that the state’s enforcement of the law is the subject of ongoing litigation with the Justice Department. But she said a federal court recently found Louisiana in violation of Section 7 of the law in a separate, private lawsuit against the state.

For all of the other concerns Vitter has raised, Appelbaum referred the senator to the inspector general’s report.

Appelbaum also highlighted a miscommunication between Vitter’s office and the Justice Department.

Vitter indicated in a news release on the day of Perez’s nomination that he first raised concerns about the National Voter Registration Act in a letter to the Justice Department sent in November 2011, and said he has been waiting for a response since then. But Appelbaum said Friday that the department never received the original letter and only learned of Vitter’s concerns in the hours after Perez’s nomination.

“The department did not receive your letter until this week, and thus we were unable to reply until now,” she wrote. “When we saw the press release your office issued on March 18, 2013, stating that the department had not responded to your letter, we contacted your office to notify your staff that we had no record of receiving the letter. We understand that your office has been unable to confirm the transmittal of this letter to the department before your staff forwarded a copy of the letter to the department via e-mail on March 19, 2013.”