Danny Kruger MP says society should be working towards ensuring good quality palliative care for everyone who needs it instead of the legalisation of assisted suicide.
Writing in The Times, the Tory MP for Devizes said pain was "rarely the main reason for assisted suicide", and that research in Oregon, in the US, showed that over half (53%) had chosen to end their lives for fear of being a burden on family and friends.
Mr Kruger, who chairs the All-Party Parliamentary Group for Dying Well, questioned the suggestion from campaigners that assisted suicide is the only way to achieve a peaceful and dignified death given the experience of using barbiturates and other powerful drugs in executions which have resulted in the "distressing and painful deaths" of prisoners.
He added that hospice care and advances in end-of-life treatments are already making it possible to "die well".
"The irony is that many people support assisted suicide because they think people should not suffer in agony at the end," he said.
"Some accounts from relatives of those who have died by assisted suicide, however, make harrowing reading. In reality recent advances in pain medicine mean no one needs to die in physical agony.
"And pain is rarely the main reason for assisted suicide."
Campaigners in the UK are pushing again for the legalisation of assisted suicide as Baroness Meacher's Assisted Dying Bill makes its way through Parliament.
The last attempt to change the law in 2015 failed.
Critics have pointed to countries like the Netherlands and Belgium, where assisted suicide has been legal for nearly two decades and where laws governing the practice have been increasingly expanded beyond terminal illness to include mental health conditions. Both countries also permit assisted suicide for children.
According to one report, the Netherlands saw record levels of euthanasia during 2020.
Mr Kruger continued, "Dignity in Dying points to Oregon as the example for the UK to follow. They never mention Canada, Belgium or the Netherlands, with good reason.
"There the state is routinely killing the frail, depressed and disabled.
"Even in Oregon, the business of death by appointment is horrible."
He concluded, "Here, surely, is the great campaign we need. Rather than licensing doctors to prescribe lethal drugs to people at the most vulnerable stage of their lives, our focus should be on ensuring that every dying person has the best possible care at the end."