A group behind the "Vote No" bloc in the smacking referendum received around $1m over six years from a conservative American religious group.
That US organisation advocates a return to "Biblical values" and its founder says "a little bit of pain goes a long way" for children.
The disclosure comes as one of the country's top Anglican clergy has condemned the attitude of Christians who claim a "God-given right" to use corporal punishment against their children.
"I am concerned that a particular stance on child discipline has too often been characterised as 'the' Christian view," said the Very Rev Ross Day, Dean of Auckland's Cathedral of the Holy Trinity.
This month's smacking referendum followed a petition initiated by Focus on the Family New Zealand programme director Sheryl Savill. An overwhelming 88 per cent of voters - 1.42 million people - voted "no" to the proposition that parental smacking be a criminal offence.
Prime Minister John Key and his Cabinet will tomorrow decide changes which, while stopping short of the changing the existing law, are expected to provide clear guidelines on when parents should be prosecuted. He has promised to "provide comfort for parents" - shorthand, it is believed, for making it clear that they will not be charged with criminal assault if they give their child a light smack.
On the strength of the referendum vote, Focus on the Family is demanding that the so-called "smacking ban" be repealed. "They need to stop criminalising good parents," said Savill at Friday night's victory party in Auckland.
Herald on Sunday investigations show that Focus on the Family New Zealand received $110,026 in "American funding", according to 2004 Companies Office reports.
Focus on the Family executive director Tim Sisarich confirmed the money came from the American parent organisation of the same name. Contributions had since increased to around $200,000 annually, he said.
Massey University Albany associate professor of history Peter Lineham said Focus on the Family has a "very controversial history in America". James Dobson founded Focus on the Family in Colorado in 1977 and became an important figure in Republican politics in the 1990s.
Focus on the Family now has annual revenues of more than $200 million and more than 1000 staff.
Lineham said Focus on the Family New Zealand often distributed literature and arguments drawn from the American "culture wars", including arguments against homosexuality and a "very masculine" approach to family life.
"Often things are taken which represent a reaction to American politics and they're turned into a moral agenda for New Zealand," said Lineham.
Focus on the Family's US spokesman Gary Schneeberger said his organisation involved itself in political debate: "We absolutely do - and certainly in the United States we have advanced Biblical values in the public square, without question."
Schneeberger said his organisation provided Focus on the Family New Zealand with funding, as well as "information and resources and counsel".
Dobson wrote a book about parenting in which he gave advice for disciplining children: "It is not necessary to beat a child into submission; a little bit of pain goes a long way for a young child."
Green MP Sue Bradford expressed concern that "an organisation associated with the conservative wing of the Republican Party is pouring resources into our domestic debate".
But Sisarich said he did not take instruction from America: "Each office is autonomous." Sisarich said, adding that Dobson had stood down from formal roles in Focus on the Family in 2003.
Larry Baldock, who helped initiate the petition, distanced himself from Focus on the Family and downplayed its role in winning the referendum.
"They didn't do a great deal of the heavy lifting," he said. "That was done by individual volunteers all over the country."