[2] Ayres worked as a union organiser in the Riverina until 2000, when he moved to Sydney.

He was elected state secretary of the Australian Manufacturing Workers' Union (AMWU) in 2010.

He defeated former federal MP Chris Haviland by a substantial margin in a ballot of Labor Left factional delegates.

[4][5] He made his first speech to parliament on 30 July 2019, in which he offered that "a cruel pea-heart beats inside the chest of this mean-spirited government".

[6] In 2022, following the ALP's victory at the 2022 federal election, Ayres was appointed assistant trade minister in the Albanese government.