Taaffe was influential in the policy decisions of Liverpool City Council of 1983–1987, according to the council's deputy leader Derek Hatton, in the formation of the Militant tendency's policy regarding the Poll Tax in 1988–1991, and the Militant tendency's "open turn" from the Labour Party in the late 1980s, becoming general secretary of Militant's eventual successor, the Socialist Party in 1997. He retired as general secretary after the party's February 2020 congress but remains on the party's executive committee as political secretary.