“If you’re not vaccinated and you’re eligible, you’re not just irresponsible, you’re an idiot,” Mr Blair said in an interview on Wednesday.
Mr Blair has made repeated interventions during the pandemic and his Institue for Global Change thinktank has been credited with devising policy proposals later adopted by the government.
When asked what he would do if he was still prime minister, Mr Blair said he was in favour of not bringing in fresh curbs before 25 December.
He told Times Radio: “I think we’ve got to be very clear with people as to why not. I don’t think it’s really that there’s some great piece of data we’re waiting on.
“It’s really because the pain of going into a full lockdown – and with this variant [Omicron] that’s the only thing that would work. And the fact that you’re dealing with people in different categories.”
He added: “The people who are boosted, double vaccinated ... or people who are completely unvaccinated. I think it’s incredibly difficult and so, right now, it is a gamble what the government’s doing ... but the public has already been through too much.”
He later told BBC Radio 4’s PM that he might have been “a little too undiplomatic in my use of language.”
Mr Blair's comments came as the current prime minister was urged to outline his post-Christmas Covid strategy, as a health minister warned there is “uncertainty” around people making new year's eve plans.
Mr Johnson on Tuesday confirmed no further restrictions will be introduced before 25 December given there is not enough evidence on the severity of the Omicron variant and hospital admission to justify stricter measures.
But with the situation being reviewed by the “hour”, Conservative frontbencher Gillian Keegan urged caution over the days ahead.
Asked on LBC about going ahead with a gathering or party on New Year’s Eve, the health minister said: “There is uncertainty. We can’t predict what the data is going to tell us before we’ve got the data.
“We are trying to take a balanced and proportionate approach so that people can see their families over Christmas to try and plan some stuff. But of course it is difficult to anticipate.”
She said the uncertainty in the data is “particularly” around severity.
But Labour pressed for decisions to be made as soon as possible. Shadow work and pensions secretary Jon Ashworth told Sky News: “People are anticipating that some form of restrictions will come in post-Christmas, and I think we just need to give people certainty.”
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