Confidentiality is a cornerstone of counselling it is put in place to protect the privacy and dignity of clients enabling freedom of expressing self in safety without fear of what you talk about being disclosed to others.  It is essential for the building of trust, rapport and sincerity within the counselling relationship; and it is in place to offer the client the control over what they chose to disclose.

Confidentiality does however have some limitations where certain disclosures are concerned for example if you were to tell me you were going to hurt yourself or another I would be bound to ensure no one gets hurts if I am in receipt of such information.  I am also bound by the law of this land and I would have to report any disclosures which were deemed to put others at risk for example children, the elderly or vulnerable adults, such acts as terrorism or the threat of, drug or human trafficking.  If I am subpoenaed by a court of law, then I may be legally bound to disclose the contents of my notes I hold of the client sessions.  

It is very rare confidentiality is breached by any counsellor, however if any of the above was disclosed to myself as counsellor I would discuss fully wherever possible any breach of confidentiality with you the client before I was to bring in a third person, however it is also deemed against the law to give a 'heads up' to a person who was deemed to be a threat to others. In some situations, where a client is deemed to be too mentally ill to be empowered to make an informed choice for themselves I will be personally bound to disclose to another for the safety of that client without discussing beforehand. 
As a private counsellor I am not bound to report to or speak with your GP, consultant, psychiatrist, psychologist or social worker, family member, friends, neighbours or anyone who may wish to have information about our relationship.  You can be confident unless you disclose anything within the limitations of confidentiality your sessions will be held in confidence once we have entered into a contracted professional relationship and what you express within our sessions will remain between you as client and me as counsellor.

We will discuss any concerns around confidentiality when we agree to enter into our professional relationship

and make our counselling contract. 
Susan Stubbings Doncaster