LONDON: Britain's public inquiry into the Iraq War said on Thursday it would not deliver its conclusions until next summer at the earliest as it seeks the release of secret government documents.

The five-member inquiry team began hearings in November 2009 and had hoped to deliver its verdict by the end of the year or early 2012. But in a statement on its website, it said that timescale was no longer possible.

“The inquiry has advised the government that it will need until at least summer 2012 to produce a draft report which will do justice to the issues involved,” it said.

“Very considerable progress has already been made, but there is still much to be done.”

The inquiry was negotiating the declassification of a “significant volume” of secret material for use in the report, or to be released alongside it, the statement said. Some progress had been made but further requests would have to be made.

“The inquiry has made clear that it will need co-operation from the government in completing this in a satisfactory and timely manner,” it added.

The inquiry, under former civil servant John Chilcot, was set up by former Prime Minister Gordon Brown to learn lessons from the 2003 US-led invasion and its aftermath.

It has heard from senior politicians, including Brown and Tony Blair, the prime minister at the time of the invasion who appeared twice, as well as former diplomats and military commanders.

When it does report, much of the focus will be on its conclusions about Blair's decision to commit 45,000 British troops to the invasion and on the legitimacy of a war in which 179 British soldiers were killed.

Critics have long argued Blair deliberately misled the public over the reason he gave for war — former Iraqi President Saddam Hussein's illegal weapons of mass destruction, which were never found.

Chilcot has repeatedly stated the aim of the inquiry is not to allocate blame, but has said it would not shy away from being critical.

“If the inquiry concludes that it wishes to criticise any individual...the individual would be informed of the inquiry's views and offered the opportunity to make representations to the inquiry,” the statement said.