Family First is expected to be stripped of its tax-free charitable status, with its director vowing to fight any such decision "right to the top".
The move would echo a preliminary ruling by the Department of Internal Affairs last year and the Charities Board's initial decision in 2013.
The independent board has been reassessing the Christian lobby group's eligibility after being directed to do so by the High Court in 2015.
RNZ understands Family First is soon to be notified that the board still intends to de-register it.
It would have another opportunity to respond before the final decision.
Charities Services has previously argued the lobby group was primarily "political" and did not advance religion or education, nor promote a benefit to all New Zealanders.
Family First would fight decision 'on principle'
Family First's director Bob McCoskrie said he would take the matter back to court and "fight this right to the top".
"We'll go to the Supreme Court ultimately if we have to, because we're fighting it on principle," he said.
"I think it's dangerous when the government determines what people can say publicly and go after some groups and not others."
The former radio talk-back host said the response was "inconsistent" and created a dangerous precedent.
"There'll be some people celebrating who oppose Family First and believe we should be censored, but our warning is - just watch out.
"One day there might be a government who disagrees with their view and will come gunning for them."
Mr McCoskrie said he believed Charities Services had targeted Family First due to the group's opposition to same-sex marriage.
"They've told us our purpose to promote and protect the traditional family is not charitable. I would just put that before New Zealanders... does that mean we should be effectively muzzled?"
A spokesperson for the Department of Internal Affairs said it could not comment while Family First's status was being reconsidered.
Family First was set up in 2006 to be "a voice of the family" with an emphasis on Judeo-Christian values.
It was a vocal opponent of same-sex marriage and anti-smacking legislation, and has more recently led campaigns against transgender bathrooms and pornography.
The non-profit organisation does not receive any taxpayer funding. In the last financial year, about $342,000 came into its coffers, mostly from donations and fund-raising.
In June 2015, the High Court directed the board to reconsider its decision, taking into account a Supreme Court ruling that recognised Greenpeace's political advocacy as a charitable act.
Organisations with charitable status do not pay income tax and can apply for various grants; their donors are also eligible for tax rebates.