David L. Strickland, NHTSA

Head of the National Highway Traffic Safety Administration David Strickland (R) stepped down from his post in late 2013. Acting Administrator David J. Friedman (not pictured) has overseen a turbulent year at the regulatory agency. (Chip Somodevilla / Getty Images)

WASHINGTON — The U.S. office responsible for monitoring safety defects in cars has had its budget stagnate and its staff cut by one-fifth from highs more than a decade ago, when Congress tried to strengthen it.

While no one has connected cuts to the failure to order a recall earlier of 1.6 million General Motors cars linked to 12 deaths, safety advocates say U.S. investigators don't have enough resources to keep up with data and detect patterns.

"They're getting information, and they're not following up," Sally Greenberg, president of the Washington-based National Consumers League said in a phone interview. "They're not capturing the information in a way that's useful. They're not responding quickly to a litany of similar complaints."

Legislation passed in 2000 amid a Ford Explorer SUV tire recall was supposed to boost the National Highway Traffic Safety Administration's defects-investigation team, adding people and giving it direct access to manufacturer data. Since then, defects that weren't pinned down for years have occurred in Toyota Motor Corp. models and now, at Detroit-based GM.

As the number of registered cars in the U.S. rose to 248 million, NHTSA's Office of Defect Investigations shrunk to 51 employees, from 64 in 2002. Its budget has been about $10 million annually since 2005, according to NHTSA.

"The idea of $10 million for an office that's in charge of the safety of all these vehicles, undertaking investigations and doing the recalls, it's just ridiculous," said Jackie Gillan, president of Advocates for Highway and Auto Safety, a Washington-based group that works with the insurance industry.

"You look at the number of people working on this, you look at their inadequate funding, and you think to yourself, no wonder this is happening over and over again."

Nathan Naylor, a spokesman for NHTSA, defended the agency's track record, saying its investigations have led to 929 recalls involving more than 55 million vehicles in the past seven years. Vehicle-related fatalities are at historic lows, and automakers have paid more than $85 million in fines since 2009 for delays in reporting defects, Naylor said in an e-mail.

The agency "pursues investigations and recalls wherever our data justifies doing so," Naylor said in response to questions about the agency's staffing. "NHTSA is constantly looking for ways to improve our process so we can better identify serious safety defects."

While Naylor didn't discuss GM, NHTSA has said it didn't force a recall sooner because the automaker hadn't provided timely information that connected defective ignition switches with failing air bags.

Legislation introduced in the Senate Tuesday would require NHTSA to publish information it collects now and do so in a searchable, user-friendly format. That would open the door for analysis of an automaker's safety data by watchdog groups, competing car companies and lawyers for accident victims.

NHTSA has been down this road before. The Transportation Recall Enhancement, Accountability and Documentation Act that emerged in 2000, amid media reports that Ford's Explorer SUVs were rolling over and killing people after their Bridgestone Corp. Firestone tires fell apart, led to a doubling of the spending on defects investigations.

The law, known as the Tread Act, also gave the regulators more information about emerging defects through quarterly reports compiling warranty claims, death and injury data from every automaker.

That was supposed to give NHTSA the raw data that companies compile and scan for anomalies that would indicate a defect. The system didn't catch the reports of faulty floor mats and sticky pedals in Toyota vehicles that became a focus of congressional hearings in 2010. It also didn't catch the GM ignition-switch defect.

"A massive information breakdown at NHTSA has led to deadly vehicle breakdowns on our roads," said Sen, Edward Markey, D-Mass., who along with Sen. Richard Blumenthal, D-Conn., introduced the legislation Tuesday to make more defect data available to the public.

GM declined to comment on the legislation.

Wade Newton, a spokesman for the Alliance of Automobile Manufacturers trade group in Washington, said the current warning system has led to more than 5,500 recalls.

"It seems premature to assume there are systemic problems, much less to identify specific legislative fixes, before investigations are complete and the data necessary for thoughtful decision-making are gathered," Newton said.

Acting NHTSA Administrator David Friedman and GM CEO Mary Barra are scheduled to testify before the House Energy and Commerce Committee on April 1.

NHTSA is under review by the Transportation Department's inspector general over how it handled events in the decade leading up to Feb. 7. That's when GM notified the agency it was recalling some models of the Chevrolet Cobalt and Pontiac G5 because of reports that jostling key rings could cause the engines to stall and air bags to fail to deploy.