Atheists in America are mimicking the high-profile advertising tactics of many churches and taking out huge Christmas billboard ads.

While churches want to attract worshippers, however, the American Atheists organisation hopes its message will have exactly the opposite effect.

The ads are aimed at atheists who might feel pressure to observe religious traditions without actually believing them, according to the organisation's president, David Silverman, who accused churches of "spewing absurdity". "Today's adults have no obligation to pretend to believe the lies their parents believed," he said. "It's OK to admit that your parents were wrong about God, and it's definitely OK to tell your children the truth."

The billboards feature a girl writing to Santa Claus saying "All I want for Christmas is to skip church! I'm too old for fairy stories."

American Atheists is particularly targeting the southern Bible Belt, with ads in the Tennessee cities of Memphis, Nashville, St Louis and in Fort Smith, Arkansas, but is having trouble finding space as the design is being rejected because of its content. It failed to secure any sites in Jackson, Mississippi, because leasing companies feared a backlash from the community.

Churches have been quick to respond to the atheist campaign. In Springdale, Arkansas, church leaders said they would put up their own billboard to compete with the atheist message. Leaders of Grace Church in Alma said they plan on putting up a billboard near the atheist advertisement, saying "Questions, Doubts and Curiosity... All Welcome At Grace Church."

The campaign echoes a similar one in the UK in 2009, which saw ads on the sides of buses reading "There's probably no God, now stop worrying and enjoy your life."