Live updates: follow the latest news on Covid-19 variant Omicron
But he argued that people should be persuaded to take the vaccine rather than be slapped with “heavy-handed” measures.
“Frankly, if you’re not vaccinated at the moment and you’re eligible and you’ve got no health reason for not being vaccinated, you’re not just irresponsible. I mean, you’re an idiot,” Mr Blair told Times Radio.
“I’m sorry, I mean, that is, truthfully, you are. Because this Omicron variant is so contagious, if you’re unvaccinated and you’re in circulation, you’re going to get it. And … that is going to put a lot of strain on the health service.”
About five million people remain unvaccinated in the UK — about 10 per cent of the eligible population.
“We shouldn’t target these people who are unvaccinated in a heavy-handed way, but we should be trying to go after them and persuade them,” Mr Blair said.
“There may be all sorts of reasons, but honestly it is in their own interest, never mind the public interest, for them to get vaccinated.”
His comments came as the UK's drug regulator, the Medicines and Healthcare products Regulatory Agency, said low-dose Covid-19 shots should be offered to vulnerable children aged 5-11.
Mr Blair criticised the delay in deciding whether to vaccinate people under the age of 12.
“I don’t know what we’re waiting for,” he said, speaking before the MHRA announcement.
The Archbishop of Canterbury, the senior bishop in the Church of England, said receiving a Covid vaccine is a “moral issue”.
“Now, obviously, there are some people who, for health reasons, can’t be vaccinated — different question — but it’s not about me and my rights to choose,” he said.
“It’s about how I love my neighbour. Vaccination reduces my chances — doesn’t eliminate — but it reduces my chances of getting ill, and reducing my chances of getting ill reduces my chances of infecting others. It’s very simple.”