Dr Peter Saunders, who is part of the group Care Not Killing, also said most people don't want the right to die, symbolised in the fact all of the British regional governments had rejected the motion in the past.
He's been speaking after Rob Marris MP, who won a private member's bill ballot last week, used the opportunity to propose new legislation to revive Lord Falconer's Assisted Dying Bill.
Lord Falconer's bill would allow a person with only six months to live to be prescribed lethal drugs, if they have a "clear and settled intention" to die, and two separate doctors agree. A High Court judge would also have powers to intervene where appropriate.
The bill ran out of time in the last parliament before it could be passed.
Most churches and Christian organisations oppose the right to die, saying man does not have the right to end life prematurely, and because states should help people to live - not to die.
Dr Saunders told Premier's News Hour: "This bill is incredibly dangerous. Its safeguards are not safe... similar legislation's been rejected several times in Westminster, and a similar bill was rejected by the Scottish parliament just a couple of weeks ago.
"The danger is that any law allowing assisted suicide or euthanasia will be open to abuse, to extension, and will put pressure on vulnerable people to end their lives."
However Pavan Dhaliwal, the Director of Public Affairs and Campaigns at the British Humanist Association thinks the bill would allow people to end their suffering early, and wants the bill to go even further, including all people suffering a terminal illness.
Ms Dhaliwal also said there needed to be "very strict safeguards" to make sure people weren't pressured into dying early, although she admitted no law is completely watertight.
She told Premier's News Hour: "We very much support Rob Marris' private member's bill, in that it would help reduce suffering of people who are terminally ill, and they wish to end their lives.
"I would go further, and say that the bill should go wider and cover those people are also incurably suffering, such as the cases of Tony Nicklinson and Paul Lamb, and there is overwhelming support for such legislation amongst the public.
"There should be very strict safeguards put into place, which of course is not beyond the wit of our policy and law makers."
The first reading of the Bill is expected to take place later this month
Listen to Dr Peter Saunders speaking on the News Hour:
Listen to Pavan Dhaliwal speaking on the News Hour: