 He entered politics as a student activist; after spending seven years in exile, he returned to South Africa in 1990.He served as general secretary of the National Education, Health and Allied Workers' Union (Nehawu) until elected to Parliament as an African National Congress (ANC) MP in 1994, where he served on the Labour, Public Service and Administration, and Finance Portfolio committees.Dexter was a member of the National Executive of the ANC, and the Central Committee and Politburo of the South African Communist Party (SACP).