Baroness Campbell, who is wheelchair bound and suffers muscular atrophy, said she already felt like she was "on the list" of those who could eventually be brought within the scope.
Lady Campbell, who sits as an independent member of the Lords, said there were already signs the safeguards could be relaxed in the future.
The final report of Lord Falconer's Commission on Assisted Dying, on which the bill is based, remarks: "We have taken on board the strong concerns expressed by many disabled people and do not consider that it would be acceptable to society at this point in time to recommend that a non-terminally ill person with significant physical impairments should be made eligible under any future legislation to request assistance in ending his or her life."
Lady Campbell wrote: "The existing law on assisted suicide rests on a natural frontier.
"It rests on the principle that we do not involve ourselves in deliberately bringing about the deaths of other people.
"What the proponents of 'assisted dying' want is to replace that clear and bright line with an arbitrary and permeable one.
"At the moment they say they want assisted suicide for people who are terminally ill, but for how long will that last, and who decides what is terminal? If terminal illness, why not chronic and progressive conditions?
"And, if chronic and progressive conditions, why not seriously disabled people?"I am already on the list. Lord Falconer himself conceded three years ago that assisted suicide should not be offered to disabled people 'at this point in time'.
"This sent a shiver down my spine: it is reminiscent of Belgium's slippery slope."Their euthanasia law is displaying an elasticity that no one could have imagined a few years ago.
"In a decade from now, do we really want to consider assisting the suicide of some of our children?"