WHOEVER thought you could weigh in on an age-old theological argument simply by getting on a bus to the shops?

But now the war over the existence of God has taken to the most unlikely of battlefields: Oxford’s buses.

The backers of an American Christian philosopher have bought advertising space on the side of 30 Stagecoach buses to challenge arch-atheist and Oxford professor Richard Dawkins to a debate at the Sheldonian Theatre next week.

The author of The God Delusion has refused, accusing William Lane Craig of “self-promotion”.

Prof Craig, who has debated other leading atheists, including journalist Christopher Hitchens, has accused Prof Dawkins of running scared.

His tour director Peter May said: “Richard Dawkins seems unprepared to defend the arguments in his bestselling book on the fifth anniversary of its publication.

“We have seen a lot of attacks by him on Prof Craig, but nothing of any actual substance.

“Does he now think his arguments in The God Delusion are indefensible?

“Craig certainly does and we hope that the bus campaign might provoke him to attend the Sheldonian and defend his book.”

The advertising slogan echoes an earlier 2009 campaign splashed over the sides of buses in London in 2009, which announced: “There is probably no God. Now stop worrying and enjoy your life.”

The new version, funded by Premier Christian Radio, says: “There is probably no Dawkins. Now stop worrying and enjoy Oct 25th at the Sheldonian Theatre.”

Prof Craig, an academic at the Talbot School of Theology in California, is regarded as a formidable debater and a staunch defender of Christianity.

Prof Dawkins has described him as a “ponderous buffoon” who uses logic to “bamboozle his faith-head audience”.

Prof Dawkins would not comment to the Oxford Mail.

But earlier this year he said he refused to debate the American because: “I have no intention of assisting Craig in his relentless drive for self-promotion.”

Organisers of Prof Craig’s “Reasonable Faith” tour will leave an empty seat on the stage of the Sheldonian next Tuesday, in the hope Prof Dawkins turns up.

Tickets for the event cost £10 from premier.org.uk