The commission had supported a man, Gareth Lee, in taking action against Ashers Baking Company for refusing to supply him with a cake iced with the message ‘Support Gay Marriage’.

Belfast County Court and Northern Ireland’s Court of Appeal had found that Mr Lee had been discriminated against on grounds of sexual orientation, political opinion and religious belief, in line with case law developed over the years.

The commission has said it is “disappointed” with the outcome of the case.

Chief commissioner Dr Michael Wardlow added: “The Supreme Court has overturned these findings and we will have to look at the implications of its judgment carefully.

“There is a concern that this judgment may raise uncertainty about the application of equality law in the commercial sphere, both about what businesses can do and what customers may expect; and that the beliefs of business owners may take precedence over a customer’s equality rights, which in our view is contrary to what the legislature intended.”