Sir John Chilcot 'understands anguish' felt by Iraq soldiers' families

The chairman of the inquiry into the invasion of Iraq is preparing to tell the families of the soldiers killed that he understands the "anguish" they are suffering, according to reports.

Sir John Chilcot will address the stinging criticism over his failure to publish the findings of the six year investigation by publicly saying that he takes his responsibility for running the probe "extremely seriously", according to the Daily Telegraph.

The delay in publication has been a growing source of frustration for Prime Minister David Cameron who has demanded a timetable for publication be set out "pretty soon".

Sir John insisted last month that his inquiry - launched in 2009 - was making "significant progress", although he could not set a date for the publication of his findings.

He is not expected to set a date for its release until after MPs return to Parliament from their summer break but the report is unlikely to be published until next year, according to the Telegraph.

Former UN weapons inspector Hans Blix has added his voice to the critics of the delays by calling for the inquiry finding to be issued "sooner than later".

He told the Telegraph: "Six years is an extraordinary long time, I sympathise with all those who feel that it has taken too long, and would like to have an honest and competent assessment.

"I would like to see it published sooner than later, the illumination of the Iraq affair is desirable. We all know that in the case of Iraq there was never any authorisation by the UN Security Council.

"The vast majority of international lawyers consider that the invasion was a breach of the UN Charter.

"We all would like to have clarity. Those who have lost people understand that even more so."

Much of the anger over the delay is focused on the so-called "Maxwellisation" process, which gives the opportunity to individuals facing possible criticism in the report to respond.

Former director of public prosecutions Lord Macdonald of River Glaven has also hit out, warning that there was "no legal justification for this crawl".

The Liberal Democrat peer told The Times that offering a right of reply to witnesses was "perhaps only fair" but said that should not mean "gifting the prize of control over the inquiry's timetable to its subjects".