I have been threatened with dismissal following disciplinary action but have been given the option of resigning. What should I do?

If you resign under threat of dismissal then it is likely that you will be found by an employment tribunal to have been constructively (ie in effect) dismissed by your employer. In such a situation you could still pursue a claim against your employer for unfair dismissal.

In the vast majority of cases, you will be better off not resigning. This then places the onus on your employer to act fairly and to have reasonable grounds for your dismissal.

One of the only reasons why you might want to agree to resign is where you have demonstrably committed an act of gross misconduct and you want to leave before you get a disciplinary record which could make it harder for you to find another job. You should only consider this drastic course of action where you have negotiated your departure using a compromise agreement, for which you will need professional advice.