The former Labour PM said if Mr Johnson is 'finding it difficult' to stick to the date for the final stage in his lockdown exit roadmap then he should consider jab-related restrictions.
Mr Blair said it 'really makes no sense to treat the two groups as if they are the same' as he insisted a two-tier system of rules would not be discriminatory.
He said provision would have to be made for people who are unable to receive a coronavirus vaccine for medical reasons.
But he suggested restricting the freedoms of people who can have a vaccine but opt not to would not be unfair because they have made an active choice to reject the jab.
Tony Blair today urged Boris Johnson to 'look again' at 'distinguishing' between the vaccinated and the unvaccinated in order to save his June 21 'Freedom Day'
There are growing fears that Mr Johnson, pictured today at the G7 summit in Cornwall, will opt to delay the final stage of his lockdown loosening beyond June 21 because of the spread of the Indian variant of the disease and increasing Covid-19 case numbers
Mr Blair's comments are likely to reignite a furious human rights and civil liberties debate over whether vaccination status should be used to determine access to society.
The UK's vaccination drive continues at pace, with the latest Government data showing that up to June 10 more than 70million jabs had been administered with just over 41million first doses.
Despite the success of the rollout, there are growing fears that Mr Johnson will opt to delay the final stage of his lockdown loosening beyond June 21 because of the spread of the Indian variant of the disease and increasing Covid-19 case numbers.
Mr Blair was asked by ITV News today what he would do regarding June 21 if he was still prime minister.
He replied: ‘They have got to look at the data as it precedes, but my point is if you do get into a situation where you are finding it difficult to keep to the June 21 date then look again at distinguishing between those people who are vaccinated and those people who aren’t because it really makes no sense to treat the two groups as if they are the same.
‘And when people say “well, you are discriminating against people who are unvaccinated”.
‘You have of course got to make provision for those people who for medical reasons can’t get vaccinated.
‘But if someone simply chooses not to get vaccinated, I mean frankly that is their choice, you are not discriminating against them, they have chosen not to do it.’
Silkie Carlo, director of the civil liberties campaign group Big Brother Watch, slammed Mr Blair's suggestion and said 'medical segregation' should have 'no place in modern Britain'.
'The idea of splitting the country into the vaccinated and unvaccinated would lead to a dystopian, two-tier, checkpoint society with no benefit to public health,' she said.