Labour says mothers and children are being punished by an outdated law which cuts women's benefits for not identifying fathers.

WINZ can dock up to $28 a week for the missing information, affecting more than 17,000 children a week.

Labour's Social Development spokesperson, Carmel Sepuloni told Rachel Smalley children are suffering because of mainly fathers who aren't fronting up and taking responsibility.

"They shouldn't be discriminated against or punished because of the deadbeat dads, as you say."

RACHEL SMALLEY: If you father a child that's your financial responsibility, not the State's

• Rachel Smalley: If you father a child that's your financial responsibility, not the State's