A Christian nurse was taken off frontline duties after she refused to take off a necklace bearing a cross.
Shirley Chaplin said she believed The Royal Devon and Exeter NHS Trust Hospital was trying to prevent her from expressing religious beliefs.
But the trust said the policy had nothing to do with the crucifix specifically, and was motivated by health and safety concerns about patients grabbing necklaces.
Mrs Chaplin, 54, from Exeter, said: "For about 30 years I have worked in the NHS and nursed patients day and night and on no occasion has my cross caused me or anyone else any injury - and to my knowledge, no patient has ever complained about me wearing it.
"The Trust even refused to test the 'breaking strain' on the necklace."
Mrs Chaplin, who is due to retire in eight months, added: "Everyone I have ever worked with has clearly known I am a Christian: it is what motivates me to care for others."
She claimed other members of staff have been allowed to wear necklaces. The Trust said necklaces of all kinds were banned but admitted there may have been "lapses".
She said: "This smacks of double standards and appears to discriminate against Christians.
"This blatant piece of political correctness amounts to the marginalising of employees' personal human rights, a blanket 'secularising and neutralising' of the NHS intended to stop Christians from expressing their faith in the public services of the NHS."
Mrs Chaplin is being supported by her minister, the Rev John Eustice, of Christ Church, Exeter, and has sought advice from the Christian Legal Centre (CLC), which has instructed human rights barrister Paul Diamond, who advised Caroline Petrie, the nurse who was suspended for offering to pray for a patient but was later reinstated.
Barrister Andrea Minichiello Williams, founder of the CLC, said: "I think members of the public, including Shirley's thousands of former patients over the years, will be astonished at the request from her employer to remove a personal item which clearly expresses something of the love and care she has for people which first led her into the nursing profession.
"You cannot separate a person's faith and motivation from other areas of their life, including what they do with the majority of their time: work.
"Unfortunately an aggressive, secularist, politically correct agenda is being driven in the NHS and other public sectors at present.
"Those wanting to promote the agenda say that it is 'neutral' but manifestly it is not.
"This agenda is leading to case after case of discrimination against Christians and real suffering.
"We will be assisting Shirley to hold out for her human rights - and expect the public en masse to do so as well."
The hospital trust said today that necklaces were banned as there was a small risk that confused patients could grab them and cause injury.
The policy was nothing to do with the cross itself which could be worn inside (not outside) her lapel - an option Mrs Chaplin was free to take up.
Mrs Chaplin was the first member of staff who had refused a request to comply with the policy, it added.
She was not threatened with the sack or disciplinary action, contrary to reports. But she was "redeployed" to a job where her own and patients' safety was not put at risk.
The spokesman said Mrs Chaplin herself had also admitted wearing a cross was not a requirement of her faith.
A spokesman for Royal Devon and Exeter NHS Trust said: "Whilst it would be inappropriate due to employee confidentiality to discuss a named individual member of staff, our uniform and dress code policy does not allow our staff to wear necklaces, with or without anything attached to it.
"We have a duty of care towards our patients and our staff, and the Trust considers the wearing of a necklace to be a risk, albeit small, within a clinical setting because patients, particularly those who may be confused, do sometimes grab for items when being moved.
"This policy was adopted after it was reviewed about 18 months ago with staff and union representatives. This is the first time a member of staff has not cooperated with a request to comply with this policy but no disciplinary action has been taken because we have endeavoured to be sensitive to personal choice, even when not a requirement of faith and when it does not comply with Trust policy for all staff.
"If a member of staff asked if they could wear a crucifix pinned on their uniform lapel this would not comply with the same policy for the same reasons but it would be acceptable to wear it if pinned inside their uniform lapel or pocket.
"We accept lapses on uniform policy may occur among our 6,000 hospital staff and line mangers are expected to address it with the individual employee."