The Government's change to the tax credit for separated parents could see neither parent get the benefit, it has emerged.

The Single Person Child Carer Credit is to replace the One Parent Family Tax Credit as part of Budget 2014.

Under the old system, both parents could claim the credit of €1,650 if a child spent time living with both of them during the year and if they were both working.

In the Budget, however, Minister for Finance Michael Noonan restricted the credit to the primary carer.

This means that, in the event that the primary carer is not working, the non-primary carer, who usually pays maintenance, will not get the credit either.

In a note clarifying a number of points in the Budget, the Department of Finance said the change had been recommended by the Commission of Taxation.

It said the original tax credit "had been available to anyone looking after a child, even if for only one night a year and even if there was no familial relationship with the child.

"This went far beyond the rationale for the credit and is unsustainable in the current budgetary circumstances."

A spokesman for the Department of Finance added that in the case of a separated couple sharing joint custody of a child either party could be nominated as a primary carer.

He said the administration would be managed by the Revenue Commissioners.

However, in the case of there being one primary carer, that person would be the only one eligible for the tax credit.