Vauxhall has been accused of a “reckless disregard for the safety” of drivers over its handling of fires affecting Zafira B models.
It was “morally reprehensible” for the car maker not to warn customers sooner, MPs on the Transport Select Committee said.
Vauxhall first became aware of a Zafira fire in 2009, and in 2014, internal concerns over a pattern in reports of fires were raised.
However, Vauxhall did not launch an investigation into the fires until August 2015, at which time 161 Zafira fires had been logged.
The fires were triggered behind the glove box in the heating and ventilation system in Zafira B models, which are still subject to a recall.
Committee chairwoman Louise Ellman said: “In this inquiry, we heard how one car manufacturer was too slow to acknowledge drivers’ concerns, too slow to begin an investigation, too slow to address the causes and too slow to alert drivers of real safety concerns.
“Drivers and their families were needlessly put at risk.
“The current voluntary approach to recalls is not robust enough.”
“Despite Vauxhall blaming the fires on unauthorised repair by third parties, no effort was made to find out where this may have taken place.
“The DVSA should consider how information to prevent improper and dangerous repairs can be collated for future vehicle safety issues.
“Finally, our inquiry exposed gaps in the system for identifying potential safety defects and dangerous repair practices.
“Only a small proportion of Zafira fires were reported to either the DVSA or Vauxhall.
“Following a Facebook campaign and use of other media, the real story emerged.”
In a statement, Vauxhall said: “We apologise to anyone who has experienced anguish or distress as a result of this incident.
“Nothing is more important to us than safety.
“We go to enormous lengths to maintain the safety of our vehicles and we have strengthened these processes further as a result of the learnings from Zafira B.”