Vauxhall showed "a reckless disregard for safety" in allowing customers to keep driving Zafira cars after a fire risk was identified, MPs have said.
It was "morally reprehensible" for the car maker not to warn customers sooner, MPs on the Transport Select Committee said.
And Vauxhall was too slow in general to take action over the fires, which came to prominence in 2015, MPs said.
Vauxhall said there were "lessons to be learned" from the Zafira fires.
The fires started behind the glove box in the heating and ventilation system, and were a problem in Zafira B cars, which are still subject to a recall.
Vauxhall 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," committee chair Louise Ellman said.
The first report of a Zafira fire was noted by Vauxhall 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 that time Vauxhall logged 161 fires.
Analysis: Richard Westcott, BBC transport correspondent
Even Vauxhall admits it was lucky that no-one was seriously hurt or worse in one of these car fires.
The MPs suggest that the company put money and reputation ahead of safety when it came to fixing the problem. The report uses damning phrases like "morally reprehensible" and "reckless disregard for safety" when describing the company's sluggish response.
It's especially scathing about the fact that Vauxhall let people drive around in cars that had been recalled and "fixed", even when engineers knew they could still catch fire.
And there's a wider issue here. Right now, there's no system in place to help owners, insurance companies, garages and emergency services report common problems so they come to light more quickly.
The full scale of the Vauxhall fires didn't emerge until a Facebook group, the London Fire Brigade and then the BBC's Watchdog programme started noticing and then highlighting a pattern.
These MPs are also calling for new laws to prosecute car makers who fail to sort a safety issue. The current system just relies on the manufacturer doing everything voluntarily.
In October 2015 a Facebook page was launched for Zafira owners that had been affected by the fires, and the BBC covered the issue in Watchdog on 22 October. A complaint was made to the DVSA about that time.
Vauxhall launched the first recall in December 2015.
In February 2016 it was told about the first fire in a vehicle that had been recalled, but it did not launch its second recall until 19 May 2016.
The MPs were particularly scathing over Vauxhall's decision to let people continue to drive vehicles that had been recalled and returned to the owners when the manufacturer knew the Zafiras could still catch fire.
"Vauxhall's decision to continue to let people drive affected cars amounts to a reckless disregard for safety. This is particularly damning given its admission that it should have notified customers earlier," the MPs said in their report.
"In the absence of any explanation for its tardy response from the witnesses that appeared before us we can only conclude that commercial considerations and the need to avoid reputational damage were put ahead of safety; this is unacceptable and morally reprehensible," they added.
The committee said that it wasn't aware of any fatalities or serious injuries caused by the fires, but they were "serious enough to destroy an entire vehicle and cause damage to other property and buildings in the vicinity".
The MPs added that the regulator, the Driver and Vehicle Standards Agency (DVSA) should be given powers to prosecute car companies that don't comply with instructions.
Vauxhall said that "there are lessons to be learned from the cases of fire in Zafira B models" as to how it investigates fires.
It said it had altered its recall process "to ensure we complete recalls swiftly and minimise customer inconvenience".
However, it said that it had "made it clear to customers" during the first recall letters "how they should operate the heating and ventilation system to keep them safe".
It added that it had made "very good progress" with the second recall.
"As of today 183,172 vehicles have had the second recall carried out and we have been working closely with DVSA as we complete the process," the car maker said.
That figure represents 79.1% of the affected cars. Vauxhall said it was aiming for a rate of 85% given that a certain number of vehicles have been stolen, seriously damaged, scrapped, exported or "sold to trade".
Industry body the SMMT said that the vehicle recall process in the UK "is one of the most comprehensive and successful in the world".