The system is flawed and unfair but it is a fallacy to think that more women at work would bring in more revenue and at what cost -both to Inland revenue and to human lives. 
 Firstly, by promoting both parents to work, leaving young children in care, there is a cost to quality of life to the entire family. Secondly, it is assumed that those extra jobs would be magically created or existing jobs re-distributed. Thirdly, it  ignores the fact that low skilled, low income workers may not have to pay tax. Yes, they may become consumers with that extra pocket money but would that make much difference to the economy and the public purse when the tax deduction or tax credit will be giving away its revenue?
There is another side to this coin and that is the fact that largely, child care is provided by immigrants. This is so particularly with regards to live-in nannies sponsored by middle and high income tax payers which means that the lower skilled immigration is increasing.