The British Medical Association (BMA) is being urged against changing its historic position on assisted suicide.
The BMA is polling doctors on whether it should support physician-assisted dying in a consultation running until February 27.
Care Not Killing, an alliance of organisations opposed to assisted suicide, is asking Christians to contact their doctors to encourage them to support continued opposition.
It warns that if assisted suicide is legalised, "vulnerable patients may feel pressure to end their lives prematurely."
"Coercion is hard to detect," Care Not Killing said.
The alliance said that in countries where assisted suicide has been legalised, "safe regulation has proved elusive" and has been unable to prevent illegal practice or abuse.
The BMA is asking its 160,000 members "whether they believe the BMA should actively support, actively oppose, or neither actively support nor actively oppose (take a neutral stance on) a change in the law" to permit doctors to "prescribe drugs for eligible patients to self-administer to end their own life" or "administer drugs with the intention of ending an eligible patient's life".
Care Not Killing said that if the BMA adopts a neutral stance, it will strengthen efforts to change the law.
"Medical neutrality would be cast by campaigners as a green light for lawmakers to weaken or repeal the laws on assisted suicide and euthanasia," it said.
"In matters of life and death, where a wealth of evidence casts grave doubts on the safety and ethics of assisted suicide, doctors must maintain clarity – by maintaining opposition."