A deputy registrar in London has written to every member of the House of Lords asking them to oppose a clause in the Coroners and Justice Bill she says would have “devastating” effects on freedom of expression for Christians in the UK.

Theresa Davies, who has worked for Islington Borough Council since 1991, is warning against the inclusion of Clause 61, which protects free speech.

She claims to have faced sustained pressure from her employers to conduct civil partnership ceremonies despite telling them that she would not do them on the grounds that they “clearly violated mandated biblical principles”.

She says she was told by employers to perform civil partnership ceremonies or be taken off her rota.

She also claims that upon returning to work after four months leave, employers gave her the option of returning to the position of receptionist or face dismissal. Her union, the GMB Union, has refused to represent her.

In her letter to peers, she says that the way she has been treated by her employers should sound “warning bells” to Lords. She believes cases like hers will become the “norm” if the Coroners and Justice Bill passes through Parliament unamended in the next few weeks.

Ms Davies says in her letter: “In a civil society, it should be axiomatic that all rights should be respected.

“There is no reason why the interests of all parties could not be accommodated; it would be perfectly possible to roster my working practices (many of my colleagues indicated a willingness to accommodate my situation) so that I only worked on civil marriages.

“The local authority responded by saying I either engage in the practices violating my conscience, or be relegated to an entry-level position of receptionist.

“The law does not require that I should be punished for my Christian faith, but that is the position of Islington Borough Council.”

Ms Davies’ case has been taken up by the Christian Legal Centre and leading human rights barrister Paul Diamond, who have decided to take legal action against the council.

Andrea Minichiello Williams, barrister and director of CLC, said: “When holding orthodox religious views at work on sexual ethics is no longer tolerated by the state, and the government fails to see the point of a free speech clause in a Bill currently before Parliament that would protect those who hold such views, we should all be alarmed.

“Everyone who cares about true democracy and the freedom to hold rich and diverse opinions in an open society should be concerned by what this case and the Coroners and Justice Bill signals - the first fruits of a closed and oppressive regime.”