US safety regulators have recorded 303 deaths when airbags failed to deploy in 1.6 million compact cars recalled last month by General Motors, according to a study released by a safety watchdog group.
The new report and higher death toll ratchet up the pressure on GM, which has said it has reports of 12 deaths in 34 crashes in the recalled cars.
GM did not recall the cars until February, despite learning of problems with the ignition switch in 2001 and issuing related service bulletins to dealers with suggested remedies in 2005.
The auto maker is facing increasing pressure to compensate victims and create a $1 billion fund, even if some would-be plaintiffs are barred from suing under the terms of GM's emergence from bankruptcy in 2009.
The Centre for Auto Safety said it referenced crash and fatality data from the National Highway Traffic Safety Administration's (NHTSA) Fatal Analysis Reporting System (FARS).
GM said late Thursday that the new report was based on "raw data" and "without rigorous analysis, it is pure speculation to attempt to draw any meaningful conclusions."
Clarence Ditlow, the centre's executive director, said, "NHTSA could and should have initiated a defect investigation to determine why airbags were not deploying in Cobalts and Ions in increasing numbers."
GM recalled the cars because when the ignition switch is jostled, a key could turn off the car's engine and disable airbags, sometimes while traveling at high speed.
The safety agency has been criticized for not pressing GM to recall the cars with defective switches, despite receiving hundreds of consumer complaints in the past 10 years and implementing its own investigations of two fatalities related to the faulty ignition switches.
US Transportation Secretary Anthony Foxx on Thursday promised an "aggressive investigation" into whether GM was slow to report to the federal government problems with ignition switches on the 2005-2007 Chevrolet Cobalt and 2003-2007 Saturn Ion.
The US attorney in Manhattan has opened a criminal probe, and House and Senate committees have pledged to hold hearings about GM and NHTSA's behaviour.
RED FLAGS IN DATA
Ditlow said the centre's study, conducted by Friedman Research Corp of Austin, Texas, also cross-referenced fatality data supplied by GM to NHTSA's Early Warning Reporting (EWR) database.
"Combining EWR and FARS data as (the centre) did should have raised a red flag to NHTSA," Ditlow said in a letter sent Thursday to the safety agency.
In a review of the EWR filings, Reuters found GM reports of three fatal crashes involving the Saturn Ion in 2003 and 2004, well before the first confirmed fatality in a Chevrolet Cobalt. Two of the three Ion crashes involved non-deployment of airbags, according to the centre's analysis of the data.
A GM spokesman on Thursday declined to provide specifics on the early warning crash reports or confirm whether the deaths in those crashes were among the fatalities counted by the company as recall-related.
GM said its investigation into the massive recall and the impact of the defective switch is "ongoing."
GM's slow recall, 13 years after the company first saw signs of a problem, is the subject of several investigations, including by Congress and by NHTSA, which investigated a 2005 crash in Maryland of a 2005 Cobalt in which Amber Marie Rose was killed.
GM engineers also were aware of four fatalities in crashes involving the 2004 Saturn Ion, GM said in filings published on Wednesday by the National Highway Traffic Safety Administration. GM did not give dates of those crashes.
The Reuters review of the Early Warning Reporting database, includes reports of at least two fatal crashes involving the 2004 Ion, one in December 2003 in Connecticut, the other in November 2004 in Texas. The database cites airbag issues in both incidents, without providing details.
A third report provided by GM to NHTSA involved the May 2004 crash of a 2003 Ion in Pennsylvania, citing engine problems, but no further details.
In a statement on its website, NHTSA said some information provided by automakers to the EWR database remains confidential, including "warranty claims, consumer complaints to the manufacturer, field reports" and the full vehicle identification number in death and injury claims.