Dr Peter Saunders, who is the campaigns director of Care Not Killing, said the country's highest court was correct on Tuesday to deny Noel Conway the right to take his legal battle further.
Explaining his opposition to allowing assisted dying, Dr Saunders told Premier: "It would inevitably lead to pressure being placed on vulnerable people - especially those who are elderly, sick, disabled or depressed - to end their lives so as not to be a burden to others; that is why the blanket ban is there."
Mr Conway (pictured in May 2018), who has been diagnosed with motor neurone disease, wants to be able to receive medical assistance to die when he has less than six months to leave and still have mental capacity.
The 68-year-old retired lecturer from Shrewsbury lost a Court of Appeal bid in June 2018 to challenge a decision by the High Court to reject his argument that a ban on assisted dying infringes upon his human rights.
He said: "All I want is the option to die peacefully, with dignity, on my own terms, and I know that the majority of the public are behind me.
"It is downright cruel to continue to deny me and other terminally-ill people this right.
Explaining their decision, the justices said only Parliament could alter the law on assisted dying. Mr Conway said supporters of legal assisted dying would campaign at Parliament for a change in the law.
Dr Saunders from Care Not Killing added: "The highest aim of government, really, is to protect vulnerable people from exploitation and abuse, and that, I'm afraid, sometimes comes at the cost of not giving liberties to those who are determined to do other things."
Click here to listen to Premier's Alex Williams speaking with Dr Peter Saunders at Care Not Killing:
Stay up to date with the latest news stories from a Christian perspective. Sign up to our daily newsletter and receive more stories like this straight to your inbox every morning.