Alastair Campbell will become the first major political figure to give evidence to the Iraq inquiry.
Mr Campbell, who was Tony Blair's head of communications in the run-up to the invasion of Iraq, will give evidence to Sir John Chilcot's inquiry next Tuesday.
It is expected that Mr Campbell will be asked about the influence he had over the Government's September 2002 dossier, setting out the case for war in Iraq.
Mr Campbell is known to have made several alterations to the dossier, which claimed that Saddam Hussein possessed weapons which could be launched within 45 minutes. Lord Turnbull, the former Cabinet Secretary, will also appear at the inquiry next week.