She is currently the associate vice-president of the External Relations and Governance Department at the International Fund for Agricultural Development (IFAD), a specialized agency of the United Nations.

Following the success of this Red-Green Coalition in the 2005 parliamentary elections, the Centre Party entered the government, and Haga succeeded Erna Solberg as Minister for Local Municipalities and Regional Development in the second cabinet Stoltenberg.

In September 2007, she became Minister of Petroleum and Energy, succeeding Odd Roger Enoksen, and leaving the regional department to Magnhild Meltveit Kleppa.

Haga replaced Cary Fowler as executive director of the Global Crop Diversity Trust in early 2013 and held that position until the end of 2019.

She is responsible for communications, global engagement, partnerships, and resource mobilization, as well as overseeing the relations with IFAD's 177 Member States.