The HCPC is the Health & Care Professions Council, which is the UK regulatory body of some healthcare professionals, such as paramedics, Occupational Therapists, physiotherapists, and radiographers amongst others. Their aim is to protect the public, hence why it is fitting they are one of the bodies to complain about their professionals conducting unscientific DWP assessments. Below is a template, which you can adapt for your use.
The address of the HCPC is: HCPC, 84-186 Kennington Park Road, London, SE11 4BU
As a regulatory body, you are set up to the protect the public, and I wish to raise this concern.
The HCPC standards require service users to be treated with respect; that you listen to service users and carers and take account of their needs and wishes. You must make sure that the safety and well-being of services users always become before professional or other loyalties. You musty make sure your conduct justifies trust and confidence in you and your profession.