[2] In May 1956, soon after his sixteenth birthday, he joined the Irish Republican Army (IRA),[3] and was politically active in Sinn Féin from an early age.

He retained his seat until the 2002 general election when he stood down in order to devote more time to his work in the European Parliament.

The party had been growing steadily in the 1980s, and had its best-ever electoral performance in the general and European elections held in 1989.

Disagreements on policy issues were exacerbated by the desire of the reformers to ditch the democratic centralist nature of the party structures, and to remove any remaining questions about alleged party links with the Official IRA, a topic which had been the subject of persistent and embarrassing media coverage.

De Rossa called a Special Ardfheis (party conference) to debate changes to the constitution.

At its founding conference in March 1992, it was named Democratic Left and De Rossa was elected party leader.

Later that year he resigned his European Parliament seat, where he was succeeded by Democratic Left general secretary Des Geraghty.

De Rossa was chair of the European Parliament's delegation for relations with the Palestinian Legislative Council.

During De Rossa's period as leader of Democratic Left, Irish journalist Eamon Dunphy, writing in the Sunday Independent newspaper, published an article alleging that De Rossa was aware, while a member of the Workers' Party, of the Official IRA's alleged illegal activities, including bank robberies and forgery.