Tony Blair's private letters to George Bush about Iraq were considered so sensitive they were expunged from the official Whitehall record, it has been revealed.
Evidence released by the Iraq Inquiry shows that No 10 officials drew up two accounts of the then Prime Minister's dealings with the US President, with all references to their correspondence being removed from the version for general circulation.
Inquiry chairman Sir John Chilcot has expressed his frustration that Cabinet Secretary Sir Gus O'Donnell had refused to clear even limited extracts from the letters for publication by the inquiry.
The assurances which Mr Blair gave to Mr Bush regarding his support for US military action against Iraq are expected to form a key element of the questioning when the former Prime Minister appears for a second time tomorrow.
The inquiry yesterday released the transcript of a closed evidence session with Mr Blair's then private secretary Matthew Rycroft who said that on a number of occasions he prepared twin accounts of conversations between Mr Blair and Mr Bush.
He said that Mr Bush would generally begin their telephone calls or video conferences in the build up to the invasion of Iraq in 2002 and 2003 by thanking Mr Blair for his latest letter.
However, Mr Rycroft said that Mr Blair had regarded them as part of a "personal dialogue" and so he had left out any reference to them in the version of the minutes which he prepared for general circulation in Whitehall.
During evidence yesterday, Mr Blair was accused by his former EU adviser, Sir Stephen Wall, of wrongly blaming former French President Jacques Chirac for the breakdown of talks at the United Nations to resolve the Iraq crisis.
He said Mr Blair had instructed his press secretary Alastair Campbell to tell journalists that Mr Chirac had threatened to veto any new Security Council resolution on Iraq, even though he knew that was not what he said.
"The Prime Minister was giving Alastair his marching orders to play the anti-French card," he said.