The British government had plans in place in case Boris Johnson died during treatment for Covid-19, the prime minister said in an interview.
Mr Johnson told the Sun on Sunday newspaper that his health continued to deteriorate during his three days in intensive care at a London hospital.
“It was a tough old moment, I won’t deny it,” he told the newspaper. “They had a strategy to deal with a ‘death of Stalin’-type scenario.
“I was not in particularly brilliant shape and I was aware there were contingency plans in place.
“The doctors had all sorts of arrangements for what to do if things went badly wrong.”
Mr Johnson, 55, returned to work on Monday, a month after he first tested positive for Covid-19.
Two days later his fiancé Carrie Symonds gave birth to their son, Wilfred Lawrie Nicholas, named partly after two doctors, called Nicholas, who helped saved his life.
Mr Johnson said that he had resisted going to hospital even though he felt groggy and “pretty wasted.”
“It didn’t seem to me to be a good move but they were pretty adamant,” he said. “Looking back, they were right to force me to go."
The premier said he went through litres and litres of oxygen as he struggled to breathe but said the worst moment was when doctors discussed putting him on a ventilator.
"The bad moment came when it was 50-50 whether they were going to have to put a tube down my windpipe," he said. "That was when it got a bit… they were starting to think about how to handle it presentationally.
"The bloody indicators kept going in the wrong direction."