In a written ruling, published on Thursday, the Strasbourg court threw out the complaint. It said not raising the Convention on Human Rights in the UK courts meant it was unable to address any potential human rights problems and it was therefore “inadmissible”.

The ruling said: “Convention arguments must be raised explicitly or in substance before the domestic authorities. The applicant had not invoked his convention rights at any point in the domestic proceedings.

“By relying solely on domestic law, the applicant had deprived the domestic courts of the opportunity to address any convention issues raised, instead asking the court to usurp the role of the domestic courts. Because he had failed to exhaust domestic remedies, the application was inadmissible.”

Paul Givan, Northern Ireland’s First Minister, said: “I am glad the European Court of Human Rights has ruled this to be inadmissible. It validates the decision of the UK Supreme Court, which was to say that this never should have been brought to court in the first place.”

He said there were “serious questions” for Northern Ireland’s Equality Commission after it had backed Mr Lee, while the Christian Institute said it was “good news for free speech, good news for Christians”.

Simon Calvert, a Christian Institute spokesman, said: “I’m surprised anyone would want to overturn a ruling that protects gay business owners from being forced to promote views they don’t share, just as much as it protects Christian business owners.”

Speaking after the ruling, Mr Lee said he had “hoped for a different outcome” and was “most frustrated that the core issues did not get fairly analysed and adjudicated upon because of a technicality”.