[5] The party has been led since 2011 by Fabian Picardo, who has served as Chief Minister of Gibraltar since the 2011 general election.

The TGWU during Bossano's tenure was instrumental in achieving parity with the United Kingdom for all workers in Gibraltar.

Bossano left the Integration with Britain Party in 1975 and founded the Gibraltar Democratic Movement (GDM), which contested the 1976 election winning four seats in the House of Assembly.

The GDM became the Gibraltar Socialist Labour Party in 1978 and obtained one seat, that of Bossano, in the 1980 election.

At the elections of 1984, the GSLP capitalized on the Gibraltarian discontent about the way the British Government was handling the future of the Gibraltar Royal Navy dockyard, opposing the transfer of the docks to Appledore International (which involved the loss of about 400 jobs), and winning seven of the fifteen seats of the Assembly.

[15] In the 2007 election to the newly named (and re-organized) Gibraltar Parliament, the party won (in Alliance with the Liberals) 31.84% of the popular vote and 4 seats.