[3][4] When New Zealand First formed a coalition with the governing National Party, Kirton was appointed Associate Minister of Health.
He then launched an unsuccessful campaign within New Zealand First to break off the coalition and come to an arrangement with the Labour Party.
Kirton did not resign from the party, however, deciding to remain a member until the end of the Parliamentary term.
He attacked his replacement as Associate Minister of Health, New Zealand First's Tuariki Delamere, as a liar, and accused him of tamely accepting whatever the National Party wished.
Later, when the coalition between New Zealand First and National finally collapsed, the government's majority became even more precarious, but it nevertheless managed to survive until the end of the term.