She joined the ALP at the age of 15 and began her involvement in the labour movement with the Sheet Metal Working Industrial Union.

[2] In 1975, Irwin became the electorate secretary to Jack Ferguson, who became the Deputy Premier of New South Wales the following year.

On 13 September she made a speech in parliament characterising Israel's policies as "ethnic cleansing" and Gaza as a "concentration camp".

[3] After criticism from Jewish groups and by members of both the Liberal and Labor parties, she issued an apology for her "offensive" language.

[4] In October 2008 Irwin publicly criticised the Rudd Government's education policy, accusing it of "locking in the Coalition's favouritism of private schools".