Watch Out

The buses will run in cities including London, Manchester, Birmingham, Glasgow, Edinburgh, York, Leeds and elsewhere, as well as parts of Devon.

In London they will coincide with a poster campaign on the London Underground with statements such as Emily Dickinson's: "That it will never come again is what makes life so sweet," and Albert Einstein's: "I do not beieve in a personal God and have never denied this but have expressed it clearly."

Many Christian groups and churches welcomed the campaign for putting God into such a prominent position in the public eye.

Paul Woolley, director of the religious think tank Director of Theos, said: "We think that the campaign is a great way to get people thinking about God. The posters will encourage people to consider the most important question we will ever face in our lives.

"The slogan itself is a great discussion starter. Telling someone 'there's probably no God' is a bit like telling them they've probably remembered to lock their door. It creates the doubt that they might not have.

"A new Theos research study, to be published next month, shows that there are as many people finding God in Britain today as losing their faith, so this campaign is speaking into a very live debate."

Mike Elms, a Fellow of The Marketing Society and former Chief Executive of ad agency Ogilvy and Mather, said that the campaign could play a role in the revival of Christianity.

Mr Elms said: "For too long, the British public has been able to dodge the 'God choice' - is there or isn't there? - by scribbling C of E on their hospital admission form. But now atheists are challenging us to make that choice one way or another. The atheist campaign opens the door toward a very public debate on the existence and nature of God."

The Methodist Church also welcomed the campaign. The Rev Jenny Ellis, spirituality and discipleship officer, said: "We are grateful to Richard for his continued interest in God and for encouraging people to think about these issues. This campaign will be a good thing if it gets people to engage with the deepest questions of life."

She disputed that thinking was anathema to religion. "As Christians, we respond to Jesus' call to love God with our minds as well as our hearts, souls and strength. Christianity is for people who aren’t afraid to think about life and meaning. John Wesley, the founder of Methodism believed that no one should be saved from the trouble of thinking, because that is the path to understanding God."

Other campaigns by the British Humanist Association include the abolition of faith schools and of the 26 bishops in the House of Lords.

Perhaps reflecting this as much as the weather, the established Church of England was frostier than its fellow Christians.

A spokesman said: "We would defend the right of any group representing a religious or philosophical position to be able to promote that view through appropriate channels. However, Christian belief is not about worrying or not enjoying life. Quite the opposite: our faith liberates us to put this life into a proper perspective. Seven in ten people in this country describe themselves as Christian and know the joy that faith can bring."

The campaign has also been picked up internationally by Spain's Union of Atheists and Freethinkers, Italy's Union of Atheists, Agnostics and Rationalists and the American Humanist Association.