Inquiry into Iraq war wants to release notes from Blair to Bush and records of conversations between Blair or Brown and Bush

The government's persistent refusal to reveal what Tony Blair told George Bush in the runup to the invasion of Iraq in 2003 is blocking any further progress on the long-awaited report of the inquiry into the war, it has emerged.

The inquiry wants to release 25 notes from Blair to President Bush; more than 130 records of conversations between either Blair or Gordon Brown and Bush, and information relating to 200 Cabinet discussions, its chairman, Sir John Chilcot, has told the prime minister.

Chilcot has told David Cameron that without a decision on what he has previously described as documents central to the inquiry, he cannot go ahead with the so-called "Maxwellisation" process.

This is the procedure whereby individuals the inquiry panel intend to criticise are given a chance to respond to the proposed criticisms before the report is finally published.

Blair is one of those most likely to be criticised for his handling of the crisis that led to the US-led invasion of Iraq with British support.

He and others were expected to be handed critical draft passages of the report this summer. But fierce opposition by Whitehall mandarins led by Sir Jeremy Heywood, the cabinet secretary, to the release of the documents has meant that the whole process is stuck in its tracks.

The inquiry panel has agreed the inquiry "should not issue those provisional criticisms without a clear understanding of what supporting evidence will be agreed for publication", Chilcot has told Cameron.

The panel has seen the classified documents but is being prevented by Whitehall from publishing them.

Chilcot said last year: "The question when and how the prime minister made commitments to the US about the UK's involvement in military action in Iraq, and subsequent decisions on the UK's continuing involvement, is central to its considerations."

The dispute over the Blair-B ush documents has been going on for well over a year. In 2011 Chilcot told Lord O'Donnell, Heywood's predecessor, that their disclosure would serve to "illuminate Mr Blair's position at critical points" in the runup to war.

Chilcot referred to passages in memoirs, including Blair's autobiography, A Journey; disclosures by Jonathan Powell, Blair's chief of staff; and the diaries of Alastair Campbell, his former head of communications. Those publications, and the refusal to disclose Blair's notes, Chilcot told O'Donnell, "leads to the position that individuals may disclose privileged information (without sanction) whilst a committee of privy counsellors established by a former prime minister to review the issues, cannot".

The latest exchange of letters between Chilcot and Cameron are published on the inquiry's website. The inquiry was set up in June 2009.