He was member of the city council, an alderman and finally burgomaster of Ninove (1995–2001). Waltniel also served as a member of parliament (Chamber of Representatives: 1965–1968, 1971–1974, Belgian Senate 1974-1992), state secretary for the civil service (1981–1985), state secretary for finance (1985), Deputy-president of the Flemish government and Flemish minister of finance and the budget (1985–1988) and Flemish minister of housing, spatial planning and monuments (1988–1992).
He was a city council member, alderman, and ultimately burgomaster of Ninove (1995–2001). Waltniel also held positions as a parliamentarian (1965–1968, 1971–1974, Belgian Senate 1974-1992), civil service administrator (1981–1985), finance minister (1985), Deputy Prime Minister of Flanders and Flemish Minister of Finance and Budget (1985–1988) and Flemish Minister of Housing, Spatial Planning, and Monuments (1988–1992).