As long as you hold Medical Council registration on the Supervised, General or Specialist Register, you must be enrolled on a Professional Competence Scheme. Your legal requirement to engage in Professional Competence is tied to your Medical Council Registration, not your employment status.
Many doctors, for various reasons, do not practise medicine for a certain period of time during their careers. Leave from practice may have an impact on your ability to meet the legal minimum Professional Competence requirements and this may then be reflected on your Annual Statement of Participation.
You are advised to maintain some level of engagement in the Maintenance of Professional Competence (MOP), however this may not always be feasible.
See:
What to do if you are absent from practice
Sabbatical or extended leave and Professional Competence
How to record an Absence from Practice
Protocol for doctors returning to work after a period of illness
Protocol for doctors returning to work after a period of absence
Why do I need to create a Personal Development Plan?