Some great answers already, I'll just add one small thing for the non-native speakers: there is a significant difference between "fired" and "laid-off". You get fired for cause; you get laid-off for a multitude of reasons, including economic.
- Being laid-off is never a concern, it has happened to untold millions of people (yes, it has happened to me too - long before consulting)
- Being fired may or may not be an issue, see previous answers
In either case, I'd be forthcoming if they ask you. Lying on an application never is the answer, and being called out for lying can (rightfully) destroy a career.