The first thing would be to refuse child grants so to prevent adults from getting children, in order to get welfare. Awarding people for getting children is wrong and stupid.

The second thing is to force mothers to reveal the father of their children. Many do not inform the state who the father is, therefore forcing the taxpayer to pay for raising the child instead of the father.

And probably the best option would be to implement policies similar to China’s one child policy. A good example would be forced sterilization after 3 children if the person receives any form government welfare (or already have kids and is imprisoned).

But in any case, well before this point, the state can spent money on voluntary sterilisation campaigns (i.e. paying the poor and drug addicts to be sterilised).