The Labour Party says it is a rort for a minister to be charging stakeholders to hear him speak.
The Christchurch branch of the ACT Party sent out invitations to a breakfast meeting to be hosted by Local Government Minister Rodney Hide, who is also the leader of ACT.
The invitation, costing $45 per head, listed Mr Hide as a minister and was sent to ACT Party members and members of local government, including Environment Canterbury.
Labour Party leader Phil Goff says it is an outrage.
"People have a right to access their minister. I've never heard of any minister charging to have him or her speak on the area that they're given responsibility for.
"That should be a right of any stakeholder in New Zealand to have access to the minister to ask questions."
Prime Minister John Key agrees that people should not be charged to hear a minister speak about their portfolio.
Mr Hide says he understands why the invite may clash with Cabinet rules and the matter is being investigated so it does not happen again.