The requirements for referees for children to be registered are as follows:

Each referee should know the child personally.
One referee should be a professional who has engaged with the child in a professional capacity, such as a teacher, health visitor, social worker or minister of religion.
The other referee must normally be the holder of a British citizen passport and either a professional person or over the age of 25.

What happens if I can't get a professional who has engaged with the child to sign as referee?

Answer from one of our lawyers:

The referees' requirements are not statutory requirements, so exceptions can be accepted, as long as you fully explain in the form or in a cover letter, your circumstances, and why you did not manage to find a referee professionally engaged with your child.
Referees must:
  • not be a relative, solicitor or agent of the applicant
  • not be related to the other referee
  • not be employed by the Home Office
  • not have been convicted of an imprisonable offence during the last 10 years
  • have known the applicant personally
  • be willing to give full details of their knowledge of the applicant
  • advise the Home Office of any reason why the applicant should not be registered.
The process for providing referee details on the online form and completing the referee declarations is described here: https://www.forum.ukcen.com/resources/uk-citizenship/naturalisation/referees/967-entering-referee-details-on-the-online-an-form

The photo that must be glued to the declaration is the photo of the applicant, in this case, the child, not the parent nor the referee.
Source: MN1 form version 02/2020.