Giles joined the ALP when he was eighteen, and – prior to his election to Parliament – worked as a principal lawyer at Slater and Gordon in Melbourne, practising in employment law.

[3] His mother was born in the United Kingdom, making him a British citizen by descent; he renounced his dual citizenship before standing for parliament in 2013.

[7] He is co-chair of Parliamentary friends of Amnesty International, and the deputy chair of the Parliament's Northern Europe group of its IPU members.

[9] In this role Giles led Labor's campaign to stop the Morrison Government's attempts to privatise Australia's visa system.

[12][13] As Immigration Minister, Giles issued "Ministerial Direction 99" in early 2023 to the Department of Home Affairs and Administrative Appeals Tribunal (AAT), which tightened the criteria for deporting non-citizen residents by focusing on their community ties and duration of time spent in Australia.

While Direction 99 had listed family violence, forced marriage, violent or sexual crimes, human trafficking, people smuggling and work exploitation as grounds for deportation, ABC News reported that the AAT and Home Affairs had ignored that part of the ruling and instead focused on deportees' ties to Australia.