But Mr Johnson said the phrase involved to large a group of people to include in the country’s first legislation for assisted dying.
He argued that it should be replaced with a phrase relating only to those who “could not reasonably be expected to survive more than six months”.
He said: “You may say there is not much difference between the two categories.
“I think the difference is very significant. It is the difference between the strong possibility of death within six months, and the overwhelming probability of death within six months.”
It came after the former Archbishop of Canterbury Dr George Carey said he did not think it was “anti-Christian” to believe terminally ill people should be allowed to die with dignity.
Meanwhile retired Anglican archbishop Desmond Tutu has also spoken out in support of giving the terminally ill the right to end their lives.
