Thanks for the accept.
Well, it is quite often seen that depression is taken a bit lightly by certain health professionals, not understanding the basis that a healthy body needs a healthy mind , and after all , it is the mind that runs your life , and if it is not at peace , then things start to fall apart.
However, having said that the best way you can ask your GP to refer you to a Psychologist for counseling is that , you tell him that your depressive condition has affected your professional as well as your personal life ,as you have been put under a lot of pressure at your job and at home for not been able to concentrate in work properly and all this you attribute to your depressive condition, and if any further delay is done in providing you the right treatment then it might just take its toll on you and it might just be too hard for you to take . So, you need to present your case to your GP, in such a way that , if you are devoid of treatment any further, then you might just break down and also make him realise that because of him taking your condition as trivial , you have already suffered a lot in your personal and professional life , make it sound in such a way that it leads to therapeutic concern in him for you, that is when he would refer you to a psychologist or may treat accordingly.
But , inspire of doing all this , if he still , does not take you seriously , then i suggest , you either seek help from another GP, or directly approach a Psychotherapist/ psychologist and present your case to him/her.