Occupational physicians and occupational health nurses have to follow ethical guidelines set by their professional organisations including the Faculty of Occupational Medicine, the Nursing and Midwifery Council, and the General Medical Council. 

These guidelines are rigorous, and are there primarily to protect you, the employee.  We have to be impartial and fair in our reports.  We do also have a responsibility to your employer, in particular for health and safety.  If we find that you are medically unsafe to undertake specific work we have to inform your employer.

Doctors who are treating you have different ethical standards; they are considered to be the 'patient advocate' so will not always be impartial when they prepare reports. If you ask them to say, for example, that you cannot undertake certain work, they may well do so even though there is no actual evidence for this. Occupational health staff will only give this advice if there is cleear evidence to support it.