Sir Keir’s position is looking increasingly precarious over the fallout which comes on top of bleak opinion poll ratings which have left MPs fearing for their seats. Ms Rayner is widely viewed as a potential successor to Sir Keir. So what do you think? Would Ms Rayner be a better PM than Sir Keir? Vote in our poll and join the debate in the comments section. Can't see the poll below? Click here.

Ms Rayner is still awaiting the findings of an HMRC review into her failure to pay the correct stamp duty on the purchase of a flat in Hove, the row which triggered her resignation from the Government in September last year.

However, the MP for Ashton-under-Lyme has significant support within the party and has long been seen as a strong candidate to replace Sir Keir.

The Prime Minister backed down from his original plans for top civil servant Sir Chris Wormald to decide which documents could not be released on national security grounds or because they could prejudice international relations.

Under pressure from Labour MPs, led by Ms Rayner, Sir Keir accepted the decision could be made by Parliament’s Intelligence and Security Committee (ISC) instead.

Sir Keir’s future has looked increasingly uncertain since admitting he knew about Lord Mandelson's ongoing friendship with convicted paedophile Jeffrey Epstein when he appointed him ambassador to the US.

He said the former business secretary “lied repeatedly” about the extent of the relationship.

On Sunday, Sir Keir’s chief of staff Morgan McSweeney stepped down, saying he took “full responsibility” for giving the Prime Minister advice that resulted in the “wrong” appointment of Lord Mandelson.

However, scrutiny of Sir Keir’s own judgment is mounting as critics, including some of his MPs, have highlighted that he made the final decision.