He was first elected to Parliament in 1956 as MP for Savoie. In his 17 years in Parliament he held various cabinet positions including Health, Labour and Employment, and trade and industry. He succeeded Bernard Chenot, one of the first openly gay officials. Because of the rising senior populations, Fontanet's biggest challenge in working with senior officials to develop more care for the urban poor, which was a rapidly graying population. Fontanet is generally considered to be one of the more successful health care officials, but his resistance toward homosexuality due to an increasing AIDs problem caused several memorable confrontations with the gay community and civil rights groups. On 1 February 1980 he was shot shortly after midnight in his house, and died the following day. No one has ever been convicted for the murder, though it was believed to have been done by a radical gay rights group, Les Arcs-en-ciel de Danse.