Former defence secretary Liam Fox has warned MPs they risk opening a "Pandora's box" if they legalise assisted dying.
Dr Fox, who worked as a GP before he was elected, said the move would fundamentally change the relationship between doctors and patients.
The Conservative MP said it was "impossible to differentiate between assisted dying and euthanasia" and "if you have one, you will inevitably get another".
"However well-meaning the proponents of this Bill may be, they will open a Pandora's box which will fundamentally change who we are and how we are as a society, how we relate to the medical profession, and I believe none of these will be to the benefit of future generations," he said.
MPs have overwhelmingly rejected the Assisted Dying Bill, despite apparent public support.
MPs are set to vote on the right to die for the first time in 20 years today as controversial laws are subject to a landmark debate.
Described by the Archbishop of Canterbury as one of "the biggest dilemmas of our time", MPs are preparing to debate assisted dying.