A Northern Ireland bakery owned by devout Christians who refused to bake a cake with a pro-gay marriage slogan was found guilty of discrimination in a Belfast court on Tuesday.

The case has become heavily politicized in Northern Ireland, with members of the province's largest political party, the Democratic Unionist Party, proposing the introduction of a Conscience Clause Bill to allow the withholding of services on grounds of religious belief.

Gay rights activist Gareth Lee took Ashers Baking Company in Belfast to court in a civil action after it canceled his order for a cake with the slogan "Support Gay Marriage" on it. The case was funded by the British province's Equality Commission.

The firm initially accepted the order but later contacted Lee to cancel it and refund his money. Lee told a court hearing over three days in March that the bakery's refusal made him feel "unworthy" and "a lesser person."

Speaking outside the court just before the judgment on Tuesday, bakery owner Daniel McArthur said: "We happily serve everyone but we cannot promote a cause that goes against what the Bible says about marriage."

In her judgment, District Judge Isobel Brownlie said the McArthurs "hold genuine, deeply held religious beliefs" but that regulations "protect people from having their sexual orientation used for having their business turned down."