What do CSA do if he denies being DS's Father

[Brightrider]

Haven't had time to post on here for some time as I had an absolutely wonderful son in January. He has just started sleeping at night so now I have some time to get a few things done.
The first of which is to try and sort things out with his father. He is still refusing to come and see him and despite all sorts of promises has not sent any money for him. in fact in his last letter ( he is refusing to speak on the phone as it upsets him too much !!!) he told me if I pursued him through the CSA he would protract things for as long as possible. As he has refused to have his name on DS birth certificate I can only assume he intends to claim he is not his father. Has this happened to anyone else and what did the CSA do?
Any advice gratefully received.

[kid]

If you still have the letter, then show this to the CSA. If he does deny being the father then you would have to have DNA test done (at a cost of about £200 I think) The test is done as a mouth swab rather than a blood test.

[beep]

if he disputes paternity the csa can ask him to take a dna test if he refuses then paternity is assumed any maintenence will be back dated to claim date,more info here csa