A code of conduct has previously been voluntarily adopted by United Future, the Greens and the Maori Party, but only relating to behaviour in the House. It was rejected by the main parties.
While a code was not a bottom line, Mr Craig said, conduct was increasingly important in light of Dirty Politics and the debate over mass surveillance.
"I'm not sure the National Party have always behaved as I think politicians should. They did go wandering through [Labour's database] ... Personally, I wouldn't do it."
He said he thought New Zealanders were being spied on.
"I have no doubt that the technology is there and the capability. My question is: are they actually using that information in any way that's inappropriate, and have we been misled on exactly what sort of information they've got? I believe we have been misled.
"The core question is can we trust our Prime Minister to tell us the truth?
He said Mr Key told the truth when it was "convenient" and had not always been straight up with the public - but the examples Mr Craig offers are not clear cut, and he seemed to become muddled over foreshore and seabed laws.
"[Mr Key] made a solid commitment on the foreshore and seabed not to proceed with that legislation if the people of the country didn't support him. He brought in the foreshore and seabed legislation. Helen Clark had ruled it out. He came in, he brought it in, and New Zealanders didn't support it."
He later said he was referring to the Marine and Coastal Area Act that National passed in 2011 to replace the Foreshore and Seabed Act.
He also accused Mr Key of going back on his word over the anti-smacking law.
"He said if good parents were being prosecuted, he'd change the law. They've been prosecuted, and he hasn't changed the law."
If the numbers fall his way on election day, Mr Craig is eyeing possible ministerial posts. He could take an associate finance or commerce role after first taking time to find his feet. He said Garth McVicar could hold an associate portfolio in justice or corrections, or even fill a new position as Minister for Victims.
It has been a steady campaign for the Conservatives so far, and support in the polls has been rising; the party was on 3.8 per cent in the latest Herald-DigiPoll survey, up from 2.6 per cent three weeks before that.
But the campaign has not been without its bumps. He has reprimanded New Lynn candidate Steve Taylor for his nasty language - "feral", "silly woman", "bitch" - about lawyers in the Family Court, and ordered that he pull his Family Court advocacy website until comments could be better moderated.
"In the Conservative Party, we don't call people names. We want to set a better standard than that."
But he has not demanded an apology, and backed Mr Taylor as being fit to be an MP; 6 to 7 per cent of the party vote would bring Mr Taylor to Parliament.
Mr Craig also claims that Mangere candidate Edward Saafi was misquoted in a media report claiming he had said the anti-smacking law was causing youth suicide.
"There's not a causative link. He's a highly qualified scientific researcher. He knows a causative link when he sees one," Mr Craig said. Dr Saafi did not respond to a request for comment.
As party support nudged higher, the vitriol from New Zealand First leader Winston Peters had become more frequent. "We're taking his vote, and I understand that hurts him," Mr Craig said.
"The guy won't ride in the lift with me. It's a bit of a strange situation. Sniping at me is actually not helping him. He'd be far better off if he made good arguments to voters. And I don't think he's helped himself, being so unclear about where he'd go [in post-election talks]."
Mr Peters' stance, however, won over one gentleman who approached Mr Craig during a walkabout in Browns Bay yesterday. He told Mr Craig: "I'd vote for you but I think John Key is arrogant and smarmy, so I voted for Winston Peters."
Another local, Ian Cooper, said he was giving Mr Craig his electorate vote, but he was party voting National because a vote for the Conservatives might be wasted.
The closer the Conservatives edge towards 5 per cent, the more convinced potential voters will be that a vote for them will count.
Contenders for Parliament
Conservative top six (if it makes 5 per cent, it will bring in six MPs)
1 Colin Craig, party founder.
2 Christine Rankin, former head of Work and Income, formerly on the Families Commission Board and the Upper Harbour Local Board, may seek a ministerial role to do with children or families.
3 Garth McVicar, farmer, founder of the Sensible Sentencing Trust, outspoken advocate for victims, hardline stance on law and order. May seek associate portfolio in justice or corrections.
4 Melissa Perkin, executive director of the Bar Association, wants to improve access to justice, including leaky-building cases.
5 Edward Saafi, biomedical researcher, stood for Destiny in 2005 in Mangere. Hardline stance on prostitution, drugs and abortion.
6 Callum Blair, local board member, former community constable, joined the party because of its opposition to the anti-smacking law.
