Have you Ever been Discharged from any Employment or Asked to Resign?
If you have been in this unfortunate situation and this is a question you are asked at interview you must ALWAYS answer it honestly.
Most employers realise that people sometimes make mistakes, its what happens next and how you dealt with that mistake that matters now.
Do not be bitter towards your former employer when you are explaining, that will come across as childish.
An potential employer will always take up your references so will find anything out that has happened in the past so this is your chance to come clean and explain your situation.
Don’t tell an elaborate tale, make sure you are factual for example:
I was dismissed as my time keeping was very poor. It was because of XYZ (please good reasons) but I understand now that I was warned several times and I deserved to be dismissed as my employer needed someone they could rely on to not be later.
If to this date you do not agree with your reasons for being dismissed then you need to explain carefully but do not sound bitter, companies have a duty to follow legal routes for these matters and will have considered all the evidence before drawing their conclusion. The person interviewing you will be well aware of this so please do not make them feel that you know better.
Be honest, admit if you did something wrong and now you want to make amends.