WASHINGTON — The acting chief of the National Highway Transportation Safety Administration, the top U.S. automotive safety regulator, is unlikely to be nominated for the job and a search is under way to fill the position, a source familiar with the matter said on Monday.

After a series of perceived failures at the administration, David Friedman, who has served this year as acting head of the agency, is not expected to be tapped by the Obama administration for the job, the source said.

The agency has been sharply criticized for responding slowly to repeated red flags of a deadly ignition flaw in millions of General Motors vehicles and its handling of recalls of millions of cars with potentially defective air bags made by Japan’s Takata Corp.

It is not clear whom Transportation Secretary Anthony Foxx and officials at the White House have in mind to run the agency. Foxx told the Detroit News a week ago a nominee would be announced soon. He did not say if the administration planned to nominate Friedman, the newspaper reported.

Rep. Fred Upton, chairman of the House Energy and Commerce Committee, on Monday said the agency needs to hold itself to a higher standard and called on new leadership.

“This can begin with the naming of a new NHTSA chief — a critically important safety post that remains vacant to this day,” Upton said in a statement.

Upton’s prepared statement came hours after the agency briefed committee staff on its handling of a problem involving Takata air bags. A similar briefing was held for the Senate subcommittee with oversight of product safety.

The House panel’s staff this week is also expected to begin a series of meetings with automobile manufacturers affected by the air bag recalls.

The Transportation Department also has launched an internal review of the agency and its response to safety lapses.

White House spokesman Josh Earnest on Monday told reporters that the agency “has been aggressive in responding to the situation related to defective air bags” but said such a review is needed to strengthen the agency’s actions in the future.

Friedman joined the National Highway Transportation Safety Administration in May 2013, after working for 12 years at the Union of Concerned Scientists, a nonprofit advocacy group. He became the acting head of the administration when his predecessor, David Strickland, resigned last December.

Friedman has spent much of this year defending the agency’s actions going back a decade. Republican and Democratic lawmakers have skewered the agency for being too cozy with automakers and for responding slowly to deadly vehicle defects.

A House report released in September found the agency had the power and information to act on GM’s faulty switches but was hampered by a “lack of knowledge and awareness regarding the evolution of vehicle safety systems they regulate.”