“Many young people who could recover with effective care might instead receive lethal medication during a period of despair,” it said.
Turner signed the letter alongside Gail Porter, the TV personality, and Stephanie Waring, the former Hollyoaks actress. All three have suffered from eating disorders.
The intervention comes as a Lords committee begins line-by-line scrutiny of The Terminally Ill Adults (End of Life) Bill.
Leadbeater’s bill seeks to allow terminally ill adults to seek medical assistance to end their lives with approval from two doctors and a three-member expert panel.
But from the start, the MP for Spen Valley’s legislative efforts have been hampered by her failure to quell concerns over the implications for eating disorder patients.
‘Overstretched and fragmented’ NHS services
The open letter, co-ordinated by the non-profit organisation Eat Breathe Thrive, and also signed by Mind, one of the United Kingdom’s biggest mental health charities, highlights international evidence that women with eating disorders have already been given assisted deaths under laws almost identical to Leadbeater’s.
One was Jessica, a 36-year-old from Colorado with anorexia and depression. When she was unable to increase her nutritional intake, her doctor deemed her illness incurable and prescribed lethal drugs.
“According to her family, she repeatedly said she did not want to die but could not continue living as she was,” the letter says.
At least 60 anorexic women are known to have died this way. The letter states they “were not individuals who were inevitably dying, but individuals whose illnesses had become life-threatening in the absence of effective treatment”.
The signatories warn that the Bill’s definition of “terminally ill”, as in Colorado, the United States, could be interpreted to include people with eating disorders who develop severe complications from starvation, vomiting or, for those who also have Type 1 diabetes, insulin restriction.
“In a health system already stretched beyond capacity, someone who is severely ill and ambivalent about treatment could be assessed as eligible for assisted death,” they said.
The letter warns peers that legalising assisted dying in England and Wales would collide with a generation of severely unwell eating disorder patients whose physical health has worsened amid “overstretched and fragmented” NHS services.
It ends with a plea for parliamentarians to take more time to consider the implications of changing the law: “We urge you to pause and ensure that legislation intended to bring compassion to those facing terminal illness does not end the lives of those who could still recover”.
Turner has previously described how pressure from studio executives to lose weight led her to develop bulimia as a teenage star.
At one point, she became so unwell that she required a live-in therapist to manage her eating while filming.
Turner played Sansa Stark for eight seasons on Game of Thrones and starred in the ITV drama series Joan, based on the life of Joan Hannington, the notorious thief.
The actor, who had two children with her former husband Joe Jonas, has said motherhood transformed her relationship with her body.
“I want this body to be around as long as possible so I can spend time with my children for as long as possible,” she told British Vogue last year.
Porter, 54, said that as a mother, and someone who has survived anorexia, she is frightened to learn young women with the same illness have been given assisted deaths in other countries.
“The evidence from abroad cannot be brushed aside,” she said. “People with eating disorders deserve support to live, and I worry this Bill could end the lives of young people who need support to recover, not assistance to die.”
Waring, 47, who has spoken about her own anorexia and bulimia, said: “When you are unwell, you can feel hopeless, frightened, and convinced there is no way out. People need treatment and understanding, not help to end their lives.”
Supporters of the Bill will be concerned that this celebrity intervention could encourage peers to run down the clock.
Almost 1000 new amendments have been tabled, more than half by just seven peers who oppose assisted dying. Campaigners for the legalisation are understood to already be worried the Bill risks running out of time if votes are forced on large numbers of these amendments.
At the first Lords committee session last week, members progressed through only two lines of the Bill.
The committee will meet again on November 21.
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