The European Court of Human Rights is hearing the cases of four British Christians who claim to have lost their jobs for religious reasons.
One of the plaintiffs is Nadia Eweida who says she was unfairly suspended by airline British Airways for refusing to remove her necklace bearing a cross.
Lawyers presenting her argument in Strasbourg claim it is discrimination.
James Dingemans, acting on behalf of Eweida, told the court: “She was working alongside colleagues who were able to wear religious symbols and attire including the Sikh turban, the Sikh bracelet, the Muslim hijab and the Jewish skull cap.”
Lawyers acting for the UK government, which claims human rights are not being infringed, say work is not the right place for religious expression.
“The Convention protects individuals’ rights to manifest their religion outside their professional sphere. However, that does not mean that in the context of his or her employment an individual can insist on being able to manifest their beliefs in any way they choose,” said lawyer James Eadie.
A ruling from the Strasbourg court is not expected for months.
It will also consider the case of a woman working for the National Health Service who had to take a desk job because of her cross.
The other two cases involve a relationship counsellor who lost his job for saying he would feel uncomfortable dealing with homosexual clients and a registrar who refused to conduct same-sex civil partnerships ceremonies.