A 23-year-old woman is being assessed to determine whether she can be killed by doctors because of her mental health problems.
Kelly, from Belgium, has applied to be killed by lethal injection after suffering for years with anxiety and eating disorders.
The UK’s Lives Worth Living campaign said the “shocking example” shows the ‘slippery slope’ of legalising assisted suicide.
Kelly applied to be killed seven months ago after being told by a psychologist that euthanasia was legal in Belgium.
She is being assessed by local professor Joris Vandenberghe.
Belgium legalised euthanasia in 2002, and since then the practice has even been extended to children.
Antonia Tully, speaking on behalf of Lives Worth Living, said that death “is not the answer to Kelly’s severe problems”.
“It’s hard not to feel that in a country where doctors are licenced to kill, there are fewer resources to treat people with Kelly’s illness.”
She added: “A caring society should be looking at ways of alleviating Kelly’s pain. If doctors in Belgium agree that Kelly can be killed, there will be even less compassion for people with profound mental health problems.”
Last month, a son who sat by his mother’s bed as she died urged UK politicians to resist pressure to change the law on assisted suicide.
In a letter to The Herald newspaper, Martin Conroy from Scotland said: “The truth is that assisted suicide gives the green light to hopelessness and despair. It sanctions suicide as a response to hardship and leaves the vulnerable more vulnerable”.
He concluded that for the good of society, the law must “uphold life and protect the vulnerable”.