Toyota is facing a severe quality crisis. The Japanese automaker has recalled millions of vehicles with potential accelerator pedal problems. Now, the 2010 version of the popular Prius hybrid is said to have brake problems.

Here are our Top 5 reasons why this crisis could lead to long-term problems for Toyota.

1. Toyota’s sluggish acknowledgment of potentially deadly problems in many of its recent models is particularly disquieting. A rapid response and immediate fix might have limited damage to its reputation. Instead, Toyota is floundering. Denial is not a strategy.

2. The pedal and brake problems undermine Toyota’s central selling point: the quality of its cars and trucks. The quality issues could uproot consumers’ long-held assumptions about high quality of the entire brand.

3. Toyota had just announced at the 2010 Detroit auto show that it planned to leverage the power of its Prius brand and extend it to other forthcoming vehicles. The questions about the quality of the Prius’ brakes threaten to derail this strategy.

4. Toyota’s U.S. competitors are getting stronger by the day. Ford is immediately positioned to benefit from Toyota defectors, and General Motors can point to its recent quality improvements as selling points.

5. Consumers aren’t convinced that Toyota knows how to fix its own vehicles. Arguments about the right way to fix the pedal problem, for example, illustrate the suspicion Toyota is engendering.