Colombo served as premier from 1970 to 1972 and was a member of the Christian Democratic Party (DC), which played a dominant role it Italian politics for 50 years, from its inception in 1944 until its undoing under the spiraling "bribesville" corruption scandal in 1994. Colombo was also active in European politics.
He served as president of the European Parliament from 1977 to 1979.
He was twice Italian foreign minister, from 1980 to 1983 and from 1992 to 1993. President Carlo Azeglio Ciampi nominated Colombo as Senator-for-life in February 2003.
In November 2003, Colombo fell under the lens of a probe into a drug and prostitution ring called "Operation Cleopatra".
Colombo admitted in front of judges to using cocaine for "therapeutic purposes" and to being gay. From 2008 onward, he joined the parliamentary group UDC-independence. Colombo was born in the southern Italian city of Potenza, Basilicata in 1920 and held a law degree.