His Majesty’s Passport Office policy on who can act as a referee is kept under review as part of the general programme of work to transform and modernise the passport application process. Any changes to the policy would be announced to Parliament and reflected in published HM Passport Office guidance.
The list of recognised professions can be found online. This is not a definitive list, and any alternatives a customer provides must be considered. Countersigning passport applications and photos: Accepted occupations for countersignatories - GOV.UK (www.gov.uk).