WATCH: Irish Bakery Won't Make Gay Bert and Ernie Cake

Northern Ireland's Equality Commission is pursuing legal action against a Belfast bakery that is claiming Christianity as justification for its refusal to decorate a cake celebrating marriage equality, according to the Belfast Telegraph.

Daniel McArthur, the 24-year-old manager at Asher's Baking Company in Newtownabbey, told a broadcasting agency that his shop does not endorse the so-called redefinition of marriage, thanks to sincerely held Christian beliefs.

"We thought that this order was at odds with our beliefs, and was certainly in contradiction with what the Bible teaches," McArthur told RTE. "And on the following Monday, we rang up the customer to let him know that we couldn't take his order. Marriage in Northern Ireland has not been redefined, it still is defined as the union between one man and one woman."

Indeed, Northern Ireland is the only part of the United Kingdom where marriage equality is not the law, notes the Telegraph.

The design the customer in this case wanted included an image of Sesame Street's Bert and Ernie, as well as text that read, "Support Gay Marriage," and the logo of an LGBT-equality group called QueerSpace.

Towleroad reports that the cake was ordered Friday by LGBT activist Gareth Lee, in recognition of the International Day Against Homophobia and Transphobia in May. Towleroad also included a video response from the bakery, produced by religious advocacy group the Christian Institute, wherein McArthur likens the company's discrimination against marriage equality supporters and LGBT people to refusing to decorate cakes with pornographic images.

Watch RTE's report on the incident below.