The Chilcot inquiry into the Iraq war will not be published until after the General Election, it has emerged.
Its chairman, Sir John Chilcot, will explain the reasons for the further delay through an exchange of letters with Prime Minister David Cameron on Wednesday, according to Government sources.
The inquiry was set up by the Labour government six years ago and heard from its final witnesses in February 2011.
It had hoped to deliver its verdict by the end of 2011 or early 2012.
Mr Cameron is understood to have written to Sir John saying that he would have liked to have seen the report released before the election, but accepted that publication was a matter for the inquiry.
The Prime Minister has spoken of his “immense frustration” at the continuing delays.
The latest news of a delay comes comes as MPs prepare to stage a Commons debate next week on the matter.
Senior Tory backbencher David Davis, a key figure in pushing for the debate, said it was “incomprehensible” that it would have to wait until the next parliament.
“Frankly this is not good enough. It is more than five years since it started,” he told The Guardian.
“We need to know why. This is not simply some formality. This is for the whole country to understand why we made a terrible mistake in Iraq. Simply putting it off is not good enough.
“Why has this taken so long? What is going on that is preventing this? The report was created in the first place by a Labour government in order to get an understanding of what went wrong. I can think of no reason why this should be deferred.”