Alastair Campbell demonstrated yesterday that he had lost none of the confrontational style and robust confidence that had made him such a crucial aide to Tony Blair.

He did, however, acknowledge that more could have been done to instil public trust in the process that led to the invasion of Iraq in March 2003.

As the first political witness before Sir John Chilcot’s inquiry into the Iraq war, Mr Blair’s former communications and strategy director was questioned on his role in preparing the government dossier of intelligence on Saddam Hussein’s weapons of mass destruction in September 2002.

Mr Campbell said that he had provided only “presentational advice” at the request of Sir John Scarlett, the chairman of the Joint Intelligence Committee. “At no time did I ask him to beef up, to override, any of the judgments that he had,” Mr Campbell said. “The whole way through it could not have been made clearer to everybody that nothing would override the intelligence judgments and that John Scarlett was the person who, if you like, had the single pen.”