Retribution: Is vengeance over Iraq the reason Corbyn won't step aside?

Mr Corbyn and ths ally John McDonnell are reportedly preparing to “crucify” their former boss for his role in leading Britain into the conflict when the 2.6m-word document.

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A number of MPs are expected to call for Mr Blair to stand trial at the International Criminal Court (ICC) in the Hague once the findings of the long-awaited inquiry are published - although the ICC appears to have ruled this out.

The issue is particularly important to Mr Corbyn, a veteran peace campaigner, whose refusal to step aside in the face of a rebellion by MPs is seen by some Labour sources to be fuelled by his hunger for retribution.

“He won’t resign until after he gets to crucify Blair over Chilcot,” one source told the Sunday Times.

Asked on Sunday whether Mr Blair may have questions to answer in the ICC, Mr McDonnell refused to rule out the possibility. “I want to see the Chilcot report, nobody can comment on this until we see the report itself,” he told Dermot Murnaghan on Sky News.

“I’m hoping that the report will be thorough and for me the importance is not Tony Blair or any individuals – it’s about the processes so we never ever get into this tragic, tragic mess again with such loss of life.”

Appearing on the same programme, Mr Blair said it was “not really appropriate” for him to talk about the report before it was published. “Let’s wait and see…there will be a very, very full debate that I will be, I can absolutely assure you, very fully participating in,” he said.