Religious freedom in the US and Europe is under threat from the courts, an Oxford professor has warned.

In his latest book, Equality, Freedom and Religion, Roger Trigg, who runs the Centre for the Study of Religion in Public Life at Kellogg College, argues: "There has been a clear trend for courts in Europe and North America to prioritise equality and non-discrimination above religion, placing the right to religious freedom in danger."

He cites a number of recent cases, including that of Lillian Ladele, the Islington registrar who refused to conduct civil partnerships because of her religious beliefs. In that case, he says, "the need to respect the right to equality trumped the freedom of religious convictions".

Ladele brought a discrimination case against Islington council in 2007 after she was disciplined. She is waiting for her case to be heard before the European court of human rights, as is a former British Airways employee, Nadia Eweida, whom bosses asked to conceal under her uniform a silver cross pendant.

Trigg says that rather than some rights being deemed more fundamental than others, those that are likely come into conflict should be more fairly balanced.

The academic, a former president of the European Society for Philosophy of Religion, complains that courts are attempting to determine the nature of religious faith for themselves. "To decide whether or not a British Airways employee could wear a cross with her uniform, the courts have suggested it is not a core part of Christian belief – but this decision shouldn't be up to them."

George Pitcher, associate priest at St Bride's, in the City of London, disagreed. "We need a bit of perspective here," he told the Guardian. "We're not being persecuted in the democratic west. To pretend otherwise is an insult to those who really are being persecuted around the world and, frankly, rather insecure and wet.

"Rather than whinge, we need to be a bit more robust about our faith. I'm not going to say it's about time my fellow Christians got off their knees, but I do wish they would stop complaining that everyone hates them. Because it's not true."

In recent years senior Anglican clerics have increasingly spoken out about attitudes towards Christianity in Britain. In 2009 the archbishop of York, John Sentamu, wrote: "Asking someone to leave their belief in God at the door of their workplace is akin to asking them to remove their skin colour before coming in to the office: faith in God is not an add-on or optional extra."

A year later, Lord Carey of Clifton said: "Christianity, which has given so much to our country, is now being sidelined as never before." The former archbishop of Canterbury has also written a book on the subject. We Don't Do God: the marginalisation of public faith is published in February.