National MP Paul Hutchison admits it was wrong of him to be reading while driving on an Auckland motorway.
The MP for Hunua was spotted driving his electorate car while looking at some papers earlier this month.
Dr Hutchison says his actions were unwise and unacceptable, and the woman who saw him was right to report him to the media.
He told Checkpoint he was heavily involved with issues regarding Auckland governance at the time and was glancing at some new information.
"I don't think it went on for too long, but it was not a good thing to do. I'm very sorry that I've done it. I don't blame her at all for dobbing me in - I think she was doing her public duty.
Dr Hutchison says he could have endangered others and regrets his actions.
Acting Prime Minister Bill English says he has spoken to Dr Hutchison and will remind all MPs in caucus that they must keep to the rules of the road.
Transport Minister Steven Joyce says it is not a good look that one of his colleagues was reading while driving.