In 1990, Dr Borg was appointed member of the European Committee for the Prevention of Torture and Inhuman or Degrading Punishment or Treatment. In this capacity he formed part of the Council of Europe delegations which visited prisons in Sweden, Italy, Greece, the United Kingdom and Bulgaria. He was a member of the Malta Environment and Planning Authority between September 1992 and April 1995.

Dr Borg was elected to Parliament in 1992, 1996, 1998 and 2003 in the interests of the Nationalist Party.

Between 1992 and 1995, he was member of the Maltese Parliamentary Delegation to the Parliamentary Assembly of the Council of Europe and was also member of the Joint Parliamentary Committee of the European Parliament and Maltese House of Representatives 1992 - 1995 and 1996 - 1998.

Dr Borg was Minister for Home Affairs between April 1995 and October 1996 and was Party spokesman for Home Affairs between October 1996 and September 1998.

Following the Nationalist Party victory at the General Election of September 1998, Dr Tonio Borg was re-appointed Minister for Home Affairs on 8th September 1998.

Dr Tonio Borg was appointed Minister for Justice and Home Affairs following the Nationalist Party general elections victory in April 2003. In March 2004, Dr Tonio Borg was elected deputy leader of the Nationalist Party and subsequently he was appointed as Deputy Prime Minister, Minister for Justice and Home Affairs and Leader of the House of Representatives by the new Prime Minister Dr Lawrence Gonzi.

Following the return to power of the Nationalist Party in the March 2008 general elections, Dr Tonio Borg was appointed by Prime Minister Dr Lawrence Gonzi as Deputy Prime Minister, Minister of Foreign Affairs and Leader of the House of Representatives.

Dr Borg is married to Adele née Galea, and they have three children Daniela, Mark and Adriana.