I had written quite a detailed reply on the difficulties of getting child maintenance and why many lone parents give up pursuing the non-resident parent, unfortunately the login facility timed out and I just hadn't the heart or time to re-do it.
Suffice it to say that obtaining child maintenance is left as the responsibility of the primary care giver; even when a court order has been obtained it is up to the claimant to pursue for non-payment. Garnishee orders are most effective but courts are reluctant to make such orders.
The simple solution is a % of income, deducted at source (like tax, prsi, health levies etc.,) and paid to the primary carer.