Labour leader David Cunliffe says he expects to be consulted on an inquiry into Judith Collins' alleged dealings with blogger Cameron Slater.
Mr Cunliffe also expected the inquiry to cast a wide net and investigate all of the allegations made against ministers and their staff in Nicky Hager's book Dirty Politics.
Prime Minister John Key launched the inquiry on Saturday after he was shown an email which suggested Mrs Collins was sharing information about then-head of the Serious Fraud Office Adam Feeley with right-wing bloggers while she was Justice Minister.
Mrs Collins denies any wrong-doing but has stood down while the matter is investigated.
Read more of the Herald's coverage:
• Calls for a full commission of inquiry
• The money men and how they toppled Collins
• Commissioner concerned by allegations
• Gallery: Collins in cartoons
• I'm the victim of a smear campaign: Judith Collins resigns
• Resignation reaction: 'Too little, too late'
• The email that brought down Judith Collins
• Collins resigns: Blogger backs mate
• Collins resigns: Jared Savage and Fran O'Sullivan respond