Michael Laws has been asked to take a paternity test to determine whether the son of his ex-girlfriend is his child.
The former shock-jock and politician has not signed the birth certificate after his former girlfriend of four years, Trina McLachlan, gave birth in July.
McLachlan, a one-time political protege of Laws, split with Laws late last year.
A friend of McLachlan's said the Department of Internal Affairs had been in contact with Laws.
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The friend said McLachlan, a student and solo mum, was being deprived of access to a Working For Families benefit because the birth certificate was unsigned.
When asked if he had declined to sign the birth certificate, Laws said he had "no information at all that would confirm what you're saying to me".
Laws said he had been subject to an "ongoing vendetta" after claiming on his RadioLive talkback show that Herald on Sunday journalists were rabid and should be shot.
Births, Deaths and Marriages registrar-general Jeff Montgomery said birth registration could affect entitlements such as inheritance and benefits. Bevan Hurley