Cain was born in Kurri Kurri, New South Wales, and attended local primary and secondary schools. He graduated from the University of Newcastle with a bachelor's degree in Mathematics (Hons), and a Diploma of Education.

Cain's early career was in teaching in NSW, South Australia and the ACT. He returned to study at the University of Canberra obtaining a Bachelor of Laws (Hons), followed by a Graduate Diploma of Legal Practice at the Australian National University.

Following graduation, Cain worked in the ACT Government in the Revenue Management Branch of Treasury, where his most senior role was managing the tax disputes section, Objection and Appeals.

He served as Vice President of the ACT Law Society from September 2017 to September 2020.

Cain was pre-selected for the Canberra Liberals' ticket for Ginninderra in December 2019. In October 2020, Cain was elected as a Member of the Legislative Assembly. Cain was appointed the following shadow portfolios; Attorney-General, Planning and Land Management, Multicultural Affairs and Assistant Treasurer. Cain's former portfolios were Regulatory Services and Jobs and Workplace Affairs, that were redistributed to other Liberal MLAs in the mid-2022 reshuffle. Cain is also an Assistant Speaker of the Legislative Assembly.

In June of 2023, Cain shared a link on his social media account X (formerly known as Twitter) calling for the Prime Minister to 'sack the ACT government'.^[2] This led the Canberra Liberals to clarify Cain's comments and deny that they want to see an end to self-government in the ACT.^[3] Chief Minister Andrew Barr said it was "a new low" for Cain, continuing by saying "[t]he Canberra Liberals are now adding democracy to the list of things they are opposed to".^[4]

Breaches to the ACT Ministerial Code of Conduct edit

In early 2024, Cain was required to apologise after it was found that he had twice breached the ACT Ministerial Code of Conduct.^[5][6][7] The document finding these breaches is entitled 'Report on the conduct of Mr Cain MLA' and was published in February of 2024.^[8]

Ken Crispin KC, the Standards Commissioner, received two complaints about Cain in later 2023.^[9][10] The first complaint and finding pertained to Cain employing his son-in-law as an intern in his office and thus 'sought to gain a benefit for a family member'.^[11][12] In the ACT it is against the law for an MLA to employ a family member as staff.^[13][14][15]

The second complaint regarded a 'misuse of public resources' when Cain sent a widespread email via his Legislative Assembly address to constituents in November 2023 that promoted a new Liberals policy.^[16] It is against the Code to use such official Legislative Assembly resources for political purposes.^[17][18] Despite findings that this email breached the Code, the Riotact reports that Cain 'took no responsibility'.^[19] Instead, Cain argued that it was his staff that sent the communication 'without my personal review'.^[20] The Standards Commissioner did not accept this reply, stating in his findings:

"[Cain] had failed to ensure that his personal staff were mindful of his commitment to the code ... To suggest Mr Cain was unaware of the email is disingenuous. It is hard to imagine that the staff initiated, crafted and disseminated the email without Mr Cain’s input or would have done so of their own accord".^[21]

The complaints were originally made by Labor minister Tara Cheyne.^[22]

Allegations Cain lied about his former career as a school principal edit

In April of 2024, the Canberra Times published a story reporting allegations from City Services Minister Tara Cheyne that Cain has not been 'upfront about his former career'.^[23] Although Cain has spoken on multiple occasions about being a school principal, Cheyne alleged in the ACT Legislative Assembly that Cain was 'never' a school principal and effectively pretended to be a principal.^[24] The allegation stems from questions pertaining to if the school Cain 'led' was properly 'registered'.^[25] In supporting the allegation, Cheyne stated:

"On the information I have I believe what I said to be true. My understanding is Mr Cain was only a principal of a school that was de-registered by the South Australian government back in the mid-1980s because it had too few students".^[26]

Cheyne was forced to withdraw the comments following a ruling from Speaker Joy Burch as the comments breached standing orders relating to personal reflections on members.^[27]

Cain is married to Claire with seven children, and lives in Belconnen. He is a practising Christian and a vegetarian.

Although unconfirmed, Peter Cain allegedly played a starring role in the 1972 arthouse film 'The Canterbury Tales' (original title: I racconti di Canterbury).^[28] IMDB's description of actor 'Peter Cain' matches that of Peter Cain MLA and states that the actor is 'married to Claire' and has 'seven children'.^[29] Despite Cain only featuring in the film for several seconds as a character named 'Absalom', the film itself features extensive nudity.^[30] The film describes itself as the 'artistic, sometimes violent, always vividly cinematic retelling of some of Chaucer's most erotic tales'.^[31]