The Department of Health in the UK has warned month that attempts by doctors or nurses to preach to other staff or patients will be treated as harassment or intimidation under disciplinary procedures.
The document, called Religion or Belief: A Practical Guide for the NHS, states: "Members of some religions... are expected to preach and to try to convert other people. In a workplace environment this can cause many problems, as non-religious people and those from other religions or beliefs could feel harassed and intimidated by this behaviour.
"To avoid misunderstandings and complaints on this issue, it should be made clear to everyone from the first day of training and/or employment, and regularly restated, that such behaviour, notwithstanding religious beliefs, could be construed as harassment under the disciplinary and grievance procedures."
Faith groups said the guidelines were so vague that they could mean action could be taken against anyone who talks about their beliefs to fellow workers or patients.
Last night Dr Peter Saunders, the general secretary of the Christian Medical Fellowship, said: "Much of the ethos of the NHS arose in a Christian environment, and many of the great pioneers in medicine were people who were motivated by a very strong Christian faith. It is quite ironic that people seem to be seeing Christian belief as something unhelpful.
"One of our cherished freedoms is that of freedom of speech, which enables us to have important debates about crucial issues. But we're seeing a culture of thought police emerging where it seems no longer acceptable to express what are really just orthodox Christian beliefs or the exercise of Christian conscience."
Neil Addison, a Roman Catholic barrister who specialises in religious discrimination cases, asked: "To what extent do you stop ordinary conversation? What they're doing is saying you cannot even talk about religion and that means a whole area of human experience is cut off."
The controversy began in December when Mrs Petrie, a community nurse, visited a patient in Winscombe, Somerset, and asked if she would like her to pray for her. Thewoman said she was "taken aback" by the suggestion and told another nurse about it.
Mrs Petrie, a Baptist from Weston-super-Mare, insists praying is just her way of saying "get well soon", but she was suspended without pay by North Somerset Primary Care Trust. It said she had breached her professional code by "promoting causes that are not related to health" and by failing to "demonstrate a personal and professional commitment to equality and diversity".
The trust carried out an internal investigation that could have led to her being sacked, but thanks to overwhelming public support, it allowed her to return to her job.
The NHS trust said: "It is acceptable to offer spiritual support as part of care when the patient asks for it. But for nurses, whose principal role is giving nursing care, the initiative lies with the patient and not the nurse."
Last night Mrs Petrie said: "I am not sure what I think about this, I want to know what conditions there are to me coming back to work."