The anti-God bus ad campaign has now spread beyond the borders of England to the heavily Catholic nations of Spain and was also scheduled to start appearing in Italy next month.
In Spain, where 94 percent of the population is Roman Catholic, buses started on Monday to carry the same atheist slogan as the London buses, according to Agence France-Presse. Buses on two routes in Barcelona display the message, "There's probably no God. Now stop worrying and enjoy your life," translated into Catalan.
Atheists in Spain say they plan to expand the campaign to the rest of the country.
Meanwhile in Italy, home of the Roman Catholic headquarters, buses with the slogan, "The bad news is that God does not exist. The good news is that we do not need him," was scheduled to start appearing in the northern city of Genoa on Feb. 4.
However, reports indicate that conservative forces in Italy have stopped the ads from appearing on Genoa buses, according to Reuters. Italian atheists affirmed recently that strong opposition from conservative political parties has caused the ad agency to pull out of the bus campaign.
"Right-wing politicians criticized us ferociously," said Giorgio Villella of The Italian Union of Atheists and Rationalist Agnostics (UAAR) to Reuters.
"It's strange that in a country where ads depicting near-naked women wearing skimpy lingerie is permitted on buses that we can't run ads about atheism," he complained.
Villella said the group's lawyer will likely file an appeal in court to overturn the decision and the atheist group will try to secure ad space in other Italian cities.
Beginning in early January, atheist ads started appearing on dozens of London buses. The campaign is funded by the British Humanist Association and is publicly endorsed as well as partially financed by atheist posterboy Richard Dawkins.
Thus far, the campaign has raised more than $195,000, or enough to fund advertisements on 800 buses across Britain, with 200 in central London alone, according to AFP. It also pays for 1,000 posters in London's underground train system and for two video screens in a popular Tube station for a full month, ending in early February.
Dawkins had told BBC in an interview that the campaign is designed to make people think, an action he claims is "anathema to religion."
Similar campaigns are being negotiated in Australia and Canada.
But in Australia, atheists are encountering some obstacles as the country's largest outdoor advertising agency, APN Outdoor, has rejected the bid by the Atheist Foundation of Australia for ad space.
There has been some resistance to the "No God" campaign, with Britain's Advertising Standards Authority (ASA) reporting some 200 complaints filed so far concerning the matter.
ASA noted that the most complaints it has ever received on an advertisement was 1,600.
Also, a Christian bus driver in London has protested the atheist ads by refusing to drive a bus with the slogan.
On Monday, he returned to work and was assured that he would not be asked to drive buses carrying the ads.
Other Christians, however, have reacted positively to the "No God" campaign, saying that it helps spark debate and provides an opportunity to talk about God.
The director of Faith-based think tank Theos, Paul Woolley, said the ads were "hardly going to be a great comfort for those who are concerned about losing their jobs or homes in the recession."
"And what does it tell us to do when we stop worrying?" he continued. "Volunteer overseas? Give money to charity? Campaign for the environment? No. It tells us to enjoy ourselves. It would be hard to come up with a more self-centered message than this."