Government ministers, civil servants and senior military figures will be expected to give evidence to the Iraq war inquiry in public and only "genuine" issues of national or personal security should prevent them from doing so, its chair has said.
The comments from Sir John Chilcot came as the inquiry announced that it would hold its first public hearings on 24 November 2009 at the Queen Elizabeth II conference centre in central London.
Details of the witnesses to the Iraq enquiry have yet to be released.
Peace campaigners have insisted that all proceedings should be in public. Definitions of what constitutes national or personal security are likely to be hotly contested - with some claiming that these categories may be used as a cover for those wishing to avoid public scrutiny.
The Prime Minister, Gordon Brown, is on record as saying that it is up to the chair of the enquiry to decide on its format, but has indicated he would be willing to appear in public.
The former Prime Minister, Tony Blair and Jack Straw, Foreign Secretary at the time of the 2003 Iraq invasion, are among those expected to be called to give evidence.
The commentator George Monbiot, who accuses Tony Blair of being "a war criminal" and a "mass murderer" has recently suggested that if he becomes president of the European Union, he may be open to legal challenge over his role in the Iraq war.