Writing in The Observer the former prime minister said Corbyn's supporters are operating in a "parallel reality" which rejects evidence and reason. Voting for the Islington North MP, he said, would be an electoral disaster.
Blair conceded he did not know what was behind "Corbynmania" and insisted that those rejecting his views are trapped in a bubble in which “reason is an irritation, evidence a distraction, emotional impact is king and the only thing that counts is feeling good about it all”.
Earlier this month Blair warned that Labour faces "annihilation" if Corbyn is at the helm and that the party was in a danger "more mortal today than at any point in the over 100 years of its existence". Weeks earlier he warned Corbyn's supporters to get a heart "transplant" or risk dragging the party back to the 1980s.
Blair compared the surge in support for Corbyn to that enjoyed by Republican hopeful Donald Trump and his Democrat counterpart Bernie Sanders, who have attracted a huge following in the US, along with Marine le Pen in France. He wrote that such movements offered a “refuge from reality”.
He wrote: “It is a vast wave of feeling against the unfairness of globalisation, against elites, against the humdrum navigation of decision-making in an imperfect world. It persuades itself that it has a monopoly on authenticity. They’re ‘telling it like it is’; when of course they’re telling it like it isn’t.”
There is only 11 days to go before the Labour party's 550,00 members will vote on whether to elect Corbyn, Andy Burnham, Liz Kendall or Yvette Cooper as their leader.