An Auckland property manager who is spending $450,000 to promote a march against the smacking law says he hopes it will be the biggest protest march in New Zealand history.

Colin Craig, 41, and his wife Helen own companies which manage high-rise apartment buildings including Nautilus at Orewa and the Sentinel at Takapuna.

He says he has never belonged to or donated money to a political party, and had never given money to the Family First lobby group until Prime Minister John Key refused to change the smacking law when 87.4 per cent of voters said in a referendum that smacking should not be a criminal offence.

But yesterday he teamed up with Family First leaders Bob McCoskrie and Bev Adair to announce plans for a "march for democracy" in Queen St at 1.30pm on Saturday, November 21.

Mr Craig will be the major funder with a budget "in the hundreds of thousands - I hope not more than $450,000".

"If this becomes a protracted battle, obviously the budget will have to be adjusted."

He and his wife have a 4-year-old daughter. Asked if he had smacked her, he said: "On occasion I've found it necessary to give her a little flick on the hand, yes."

But he said his motivating force was the principle of democracy rather than the smacking law.

"My involvement came out of discussions with friends saying we don't think it's right for such a considerable majority of voters to be ignored. That prompted me to look at what I could do about it."

He said his wife fully backed the decision to put much of their savings into the march.

"I'm Scottish by background. I'm married to someone who's half-Scottish and half-Jewish," he said.

"I'm never going to own a boat, but some things are more important."

A family friend, North Shore fulltime mother-of-two Shelley Vitali, is acting as the march's unpaid media liaison officer, other volunteers have been enlisted, and Mr Craig said he hoped ordinary New Zealanders would turn out.

"The reality is if we have the biggest protest march in the history of New Zealand, which I'd love to know how big it was ... [we can't be ignored]," he said.

"The [2004] hikoi got more than 10,000. The [2005 Destiny Church] march for family values got close to 15,000. I'm absolutely hoping to get an awful lot more than that."

However, the author of the political history No Left Turn, Chris Trotter, said recent protests came nowhere near the biggest historical turnout of 50,000 to 70,000 people for an Auckland Domain rally by Labour politician John A Lee before the 1938 election.

* Biggest marches

1932: Unemployment march ("Queen St riot"), 15,000.

1938: J. Lee rally, Auckland Domain, 50,000 to 70,000.

1971: Vietnam war march, Queen St, up to 35,000.

1981: Against union militancy, Queen St, 30,000.

1981: Springbok tour mobilisation, Queen St, 25,000.

2001: Anti-GM march, Queen St, 10,000.

2003: Iraq war protest, Queen St, 10,000.

2004: Foreshore seabed hikoi, Wellington, 15,000.

2005: Destiny Church march, Queen St, 10,000.