Petition Childcare costs should be considered as an expense by the CSA

The CSA calculations for maintenance payments from the absent parent does not include childcare costs - merely maintenance costs. This means that should the primary carer wish to work full time, they are penalised for working - in my case £9000 a year for one child, whilst the other parent can work full time and needs to pay nothing towards childcare as it is perceived that the tax credit system should step in and help.
Why shouldn't the absent parent pay their fair share of childcare costs and why should the state make up the shortfall?
The CSA should take child care costs into account when calculating the monthly payments.