A New Zealand minister has given his support to an atheist campaign asking people to question the existence of God.

Archdeacon Glynn Cardy, vicar of St Matthew-in-the-City in Auckland, says NZ Bus's decision last month to stop the display of paid adverts showing atheistic slogans is regrettable.

"Many in the Christian community welcome a debate about issues of the existence of God and, also, I don't think there's anything to be afraid of in that debate," he said.

The NZ Atheist Bus Campaign has raised nearly $23,000 from public donations for the ads that read: "There's probably no God. Now stop worrying and enjoy your life."

Similar campaigns have run in Australia, the United States, Britain and several other European countries.

NZ Bus tentatively approved the ads for buses in major centres, but backed down after receiving complaints from the public and staff.

Archdeacon Cardy, who last year put up a controversial billboard outside his church showing the Virgin Mary and Joseph in bed, hoped NZ Bus would review its decision.

"Free speech should be the norm, censorship the exception. I don't see it as a negative thing at all. I think it brings God into public debate."

He said bus advertising was used to promote a whole range of products from clothing to alcohol.

"How refreshing it is to see advertising that is not asking us to buy anything, aspire to be slim, or sell us a lifestyle we can't afford.

"I suspect if a mainstream religious group wanted to put a billboard on a bus and fund it, there probably wouldn't be any objection."

Simon Fisher, spokesman for the Atheist Bus Campaign, said he had received emails and blog posts from Christians supporting the ad, in particular backing the group's right to freedom of speech.

"He [the archdeacon] seems to be mirroring the opinions of quite a few people out there," said Mr Fisher.

But not all religious groups were so supportive of the bus campaign.

Lyndsay Freer, spokeswoman for the Auckland Catholic Diocese, said NZ Bus made the right decision by turning down the ads and described the campaign as disturbing and concerning.

"Whether one's faith is Christian or Muslim or Jewish or various other faiths, the majority of New Zealanders do have a personal belief in God, however they understand God."

Ms Freer said it was an interesting campaign because it did not take a strongly atheistic stand with its use of the word "probably".

"They're hedging their bets."

The NZ Atheist Bus Campaign has not heard from NZ Bus, but Mr Fisher said he did not expect to.

His group was examining its options and the legal process of going through the Human Rights Review Tribunal appeal process.

"We need to jumpstart that process and then we'll be able to decide if we want to launch the whole legal thing - otherwise just change mediums."

Mr Fisher said he could only speculate on why NZ Bus turned down the advertisement when so many others had gone ahead.

Siobhan O'Donovan, communications manager for NZ Bus, said: "We have no further comment to make at this time."

Meanwhile, Archdeacon Cardy said reports he was leaving St Matthew-in-the-City were untrue.

The appointment of Ross Bay as the new Anglican Bishop of Auckland meant all the archdeacons had to resign and re-apply for their positions.

Archdeacon Cardy said he would reapply and intended to stay with St Matthew.