my wife as nothing to do with my failed business,and all debt are in my sole name,she dosent work but child tax credits come in her name,is this classed under my income
No, if you declare BR then the OR will go though your I&E and may ask if your wife contributes to the monthly expenses but cannot force her to contribute.
I am not sure about child tax credits but child benefit isn't counted as disposable income as it is taken for granted that this money goes towards food/clothing of the child(ren).