LONDON (RNS) Rejecting protests by Christian groups, Britain’s advertising watchdog agency has given the go-ahead to a campaign to plaster atheist signs on hundreds of buses and other vehicles across the country.

The Advertising Standards Authority ruled that the campaign, which uses the slogan “There’s probably no God,” was unlikely to mislead or “cause serious or widespread offense.”

The ASA is a powerful regulator set up as a self-governing agency for the nation’s advertising industry, with the authority to take its cases to the government’s Office of Fair Trading. As such, its decisions are rarely, if ever, challenged.

The $100,000 ad campaign is sponsored by the British Humanist Association. The signs, in full, say, “There’s probably no God. Now stop worrying and enjoy your life.” The ads will be placed on some 200 buses in London and on 600 other vehicles in England, Scotland and Wales.

The campaign has prompted one Christian bus driver, Ron Heather of Southampton, England, to walk off the job in protest. When he first caught sight of the banner, Heather said, “my first reaction was sheer horror.”

He added that “it was the starkness of this advert which implied there was no God” that got to him, and that “I felt that I could not drive the bus.”

But Hanne Stinson, chief executive of the British Humanist Association, told reporters that “I can’t understand why some people have a different attitude when it comes to atheists.”

Most of the 326 complaints that the ASA received were from Christian organizations and individuals, who said the slogans denigrated people of faith. Others argued that the advertiser could not substantiate its claim that God “probably” does not exist.

However, the ASA said the ads amounted to an expression of the advertiser’s opinion and that its claims were beyond objective substantiation.