He served as a Cabinet minister while in the Labour Party and has since done so in governments dominated by the centre-right National Party as well as by the Labour Party. From 2005 to 2008 he held the posts of Minister of Revenue and Associate Minister of Health as a minister outside of Cabinet with the Labour-led government. After Labour suffered an election defeat in 2008 to the National Party, United Future was reduced to having Dunne as its sole MP. However, in a deal between United Future and National, Dunne retained his two portfolios outside Cabinet. On 7 June 2013 he resigned his warrant as a minister due to a purported leak from his office. He effectively was an independent MP between 25 June 2013 and 13 August 2013 when United Future was temporarily deregistered. On 28 January 2014 Dunne was reinstated as a minister holding the Internal Affairs, Associate Health, and Associate Conservation portfolios.