Alastair Campbell and Sir Andrew Turnbull, the head of the Civil Service, are to be summoned before a powerful committee of MPs to answer questions on the treatment of Dr David Kelly.
Mr Campbell, who had earlier refused to appear before the Public Administration Committee, will be asked about Downing Street's role in releasing Dr Kelly's name to the press. He is expected to be called next week when MPs return to the House.
It would be Mr Campbell's first appearance on the political scene since standing down as the Prime Minister's director of communications and strategy. Now that he has left Number 10, he may not be able to refuse a summons.
Mr Campbell would be questioned as part of the committee's review into the Government's communications policy. The Public Administration Select committee has already asked Sir Andrew, the most senior civil servant in Whitehall, to appear and explain whether the Civil Service, as Dr Kelly's employer, abided by its "duty of care" to the scientist.
Dr Kelly apparently committed suicide after he was named by the Government as a source for a BBC story about an intelligence dossier on Iraq's weapons of mass destruction.
The cabinet secretary is understood to be cautious about the invitation and his office is negotiating with the committee on the terms of his appearance and the date.
"Why wasn't the head of the Civil Service involved in the whole issue of how to treat Dr Kelly?" asked one source close to the committee.
The Hutton inquiry into the death of Dr Kelly will take evidence today from Sir Kevin Tebbit, the permanent secretary at the Ministry of Defence.Reuse content