Backers of the petition to reverse New Zealand's internationally "acclaimed" anti-smacking law-change are confident they will gain enough signatures, despite failing at first.
"We're confident we can do it," Kiwi Party leader Larry Baldock said last night.
But opponents of the petition urged its backers to accept the new law, which they said was working well.
The organisers have two months from yesterday to gain the number of valid signatories required to force a non-binding referendum at this year's general election on the petition's question: "Should a smack as part of good parental correction be a criminal offence in New Zealand?"
The petition needed 285,027 valid signatures - 10 per cent of registered voters - when it was presented to the Clerk of Parliament on February 29.
The organisers gathered 324,316 signatures, but after a check, only 269,500 signatures were considered valid - a shortfall of more than 15,000.
Of the 29,501 signatories checked, 3373 could not be found on the electoral roll, 214 were illegible, 158 were duplicated and two had signed three times.
Mr Baldock said the authorities had miscalculated and the Auditor-General should review the matter. But a further 20,000 signatures had already been gathered, and he was confident of gaining many more that, to ensure there were enough, even if the sample checked next time had a greater proportion rejected.
Gordon McFadyen, general manager of the Children's Commissioner's office, said the pro-smacking lobby's failure to gather enough signatures showed a referendum was not needed.
"Since New Zealand revised its law ... a further five countries have now banned physical punishment of children ... New Zealand's stance on protecting our children from violence is acclaimed internationally and the law-change is something we should be very proud of."
Green MP Sue Bradford said her party supported Mr Baldock's democratic right to continue with the petition, but the time and money could be used to promote children's interests in other ways.
"I don't believe there is an appetite among political parties or the public for making the physical punishment of children lawful again."
But the Family First group said the number of people who signed the petition showed that politicians should amend the anti-smacking law "to leave good parents alone" now, not after the election.