Christians at a Devon university are threatening legal action against their students' union because of a row over equal opportunities.
Exeter University's Guild of Students says the Christian Union (CU) is not open to all - because members must sign a form saying they follow Christ.
The guild said some privileges afforded to societies had been suspended because of the CU's constitution.
The CU said it was challenging the ruling under Human Rights laws.
The 50-year-old CU said in a statement that it had been temporarily suspended from the official list of Guild of Students' societies.
The CU said it appeared that unless it disassociated itself from the Universities and Colleges Christian Fellowships, and stopped asking committee members and speakers to sign a declaration, it could be permanently banned from the guild.
The declaration includes the phrase: "In joining this union, I declare my faith in Jesus Christ as my Saviour, my Lord and my God".
Guild of Students President Jemma Percy said the requirement to sign the declaration meant "participation in the society was not open to every student".
She said: "We have a duty to represent them and uphold equal opportunities."
She added that the union had not been suspended: "The ECU remains one of our 109 societies."
The CU on Tuesday sent a letter to the guild advising that legal proceedings would start after 14 days unless its was fully re-instated as a student society.
Action would be taken under the Human Rights Act and the Education Act 1986, said the CU - which has retained a barrister.
"This is a fundamental issue of freedom of speech and of common sense," said CU worker Emma Brewster.
She added: "Legal action is the last thing we want to take."
The CU was told to change its name after a vote involving 899 of the 13,800-strong student body saying it should be known as the Evangelical Christian Union.