Downing Street communications chief Mr Alastair Campbell is to give evidence next week to the inquiry investigating the death of government weapons scientist Dr David Kelly.
Mr Campbell - who is expected to face questions over a BBC report claiming he was responsible for having "sexed up" the Government's dossier on Iraqi weapons - will appear before the inquiry on Tuesday.
He will be followed on Wednesday by the Prime Minister's official spokesman, Mr Tom Kelly, who described Dr Kelly as a "Walter Mitty"-style fantasist.