An atheist organisation is threatening to sue a Searcy, Arkansas pizza shop over the restaurant's church bulletin discount.

Bailey's Pizza offers 10 per cent off a customer's order on Sundays if they bring a church bulletin, and the Freedom From Religion Foundation (FFRF) is accusing them of discrimination.

Christian small business owner Steven Rose opened the pizza parlour with his wife in July. He said the discount was not a religious message, but a way to bring in customers.

"It was a straight-up marketing tool to give a discount to people I love and care about – and have them come in and have lunch with me," he told Fox News. "I thought it was a sweet idea. I didn't say you had to go to church to get it. Go get a bulletin from your neighbour and come in and have a pizza."

News of the discount spread to Facebook, and reached the attention of atheist advocacy organisation FFRF.

"The law requires places of public accommodation to offer their services to customers without regard to race, colour, religion or national origin," FFRF spokeswoman Elizabeth Cavell told KTHV.

The Liberty Institute, a conservative Christian legal defense organisation, said the FFRF is misapplying the Civil Rights Act.

"If what FFRF is saying were true, restaurants and other businesses would be precluded from giving veterans and military members discounts because that would technically be discriminating based on veteran status," Liberty Institute Director of Litigation Hiram Sasser told Fox News.

"Is that what FFRF wants? Give me a break!"

In addition to the church bulletin discount, Bailey's Pizza allows patrons to write Bible verses on their walls. The restaurant prominently displays the message: "God is the centre of our lives, so our scripture wall is the centre of Bailey's Pizza."

Rose said he will continue to use his business to glorify God.

"To me, if making a pepperoni pizza furthers the Kingdom – well I'm excited about that," he said.

"As for me and my house, we'll serve the Lord."