Vidar has held a number of posts both in the AUF (Young Labour Party) and in the Oslo Labour Party. These posts have included being a member of Oslo Town Council (1987 to 1991), leader of Oslo AUF (1990), leader of Kampen and Vålerenga Labour Party (1994-1995) and member of the executive committee of Oslo Labour Party (1996).

He was also regional secretary in Finnmark AUF (1986), regional secretary in Oslo AUF (1986-1987), political secretary in Oslo Labour Party (1988-89) and city council for children and education in Oslo (1992-1993). Vidar is a Postgraduate in social economics at the University of Oslo (1996). As he was appointed State secretary he held a position as Deputy Director General in the Ministry of Finance.

Vidar is living in Oslo, with his partner.