Barrett also contested the 2021 Dublin Bay South by-election for the National Party, receiving 183 first-preference votes (0.68%), thus failing to be elected.

His early activism focused mostly on campaigning in Irish referendums from a Eurosceptic, anti-abortion, anti-immigration, and social conservative perspective.

[18] In September 2019, he controversially implied that, if in power, he would strip the Irish citizenship rights of local government politician Hazel Chu, in spite of the fact she had been born in Ireland and lived there for her entire life.

[27] In April 1999, Barrett and seven other Youth Defence members were convicted of public order offences for a protest described at the time as a "mini-riot" outside the Adelaide Hospital that had taken place on 16 May 1998.

Barrett, then 31 years-old, established the No to Nice campaign with Rory O'Hanlon, a retired High Court judge.

Barrett initially denied, and subsequently admitted that he had spoken at an event organised by the NPD,[33][34] a far right, ultranationalist political party.

Justin Barrett has always claimed that he spoke at these events in an anti-abortion capacity on behalf on the Youth Defence Organisation.

[35] Gerry McGeough, a former Provisional IRA volunteer and Sinn Féin national executive member, defected to Barrett's campaign.

Barrett employed nationalist rhetoric during his campaign and stated his intention to "put Ireland first" in the European Parliament.

Later that year, while attending an immigration debate at University College Dublin's Literary & Historical Society, Barrett was assaulted by attendees allegedly belonging to an Irish anti-fascist group.

The debate was chaired by popular RTÉ radio presenter Joe Duffy, and featured Áine Ní Chonaill of Immigration Control Platform.

[49][50][51] In October 2019 he addressed a community meeting in his hometown of Borrisokane on plans to open up a direct provision centre for 80 asylum seekers.

[63] In June 2021, he announced he would be running for public office for the first time as leader of the National Party, in the 2021 Dublin Bay South by-election, caused by the resignation of Eoghan Murphy.

[69][70] Entitled The National Way Forward!, in its text he described immigration as "genocidal", and cited Hilaire Belloc, G. K. Chesterton and Arthur Penty as having been influential figures in his philosophical development.

[80] Of particular attraction was the participation of... the leader of the National Alliance from the USA, Dr William Pierce and, last but not least, the leader of a noteworthy Irish anti-abortion group, Justin Barret (sic) from Youth Defense (sic).The National Party and Barrett have stated that he addressed meetings all across Europe in his capacity as an anti-abortion speaker.

[81]A leading far-right politician in Germany has described the anti-abortion group Youth Defence as "an important part of our international network".

The German authorities say the JN began to take on neo-nazi characteristics in 1996.In June 2001, the website of neo-Fascist group Forza Nuova reported that Justin Barrett had attended a number of their events in Italy (in Milan, and Bologna).

A group of Forza Nuova students, led by the then 25-year-old Marco Gladi, visited Ireland in 2001 to "study" with Youth Defence.

In an editorial on the Forza Nuova website, the movement calls itself a "friend" of Mr Barrett and praises his efforts to defeat the Nice Treaty.

[83][84][85][86] As part of the dirty war waged by "liberals" against "nationals", the greatest exponent of the nationalist front Justin Barrett, he was attacked in a press campaign of the kind to which we were accustomed us in the past.

FN and NPD are, in the mind of the accusers, friends whose Barrett should be ashamed[87]In 2017, during the party's first ard-fheis held at the Trump International Golf Links and Hotel Ireland, Barrett stated that the National Party was "only for straight Irish people" and defended perceived homophobic comments made by James Reynolds, causing guest speaker John Wilson to walk out of the event in protest.

O'Gorman had been attacked by members of the Irish far-right on social media after his appointment as Minister for Children, due to tweeting a photo of himself with Peter Tatchell at a Dublin Pride parade in 2018.

[89] O'Gorman said that he was unaware of the views expressed by Tatchell 20 years previously, stating he "probably would have re-considered taking a photo with him" had he read the 1997 letter before the march.

Barrett was investigated by Gardaí for alleged road traffic offences and breach of COVID-19 pandemic travel restrictions.

[94] In October 2021, in an appearance before Longford District Court, he was charged with driving without a licence or insurance, and with failing to produce both documents and an NCT certificate within ten days.

[95] Arising from the same incident, which occurred in Clonfin, County Longford, he was also accused of engaging in threatening and abusive behaviour contrary to the Public Order Act.

[21] On 9 November 2023, Barrett appeared at an anti-immigration protest outside Leinster House wearing a Nazi SS uniform.

[98] He was denounced in a statement published by the National Party for engaging in a "pathetic publicity stunt" described as "an effort to discredit the protest and grab a headline for himself.

[107] In November 2020, she responded to a tweet by then-Lord Mayor of Dublin Hazel Chu, placing a fake order for Chinese takeaway food with "no bat".

[108] Both Justin and Rebecca Barrett have reportedly posted "pro-Hitler content on [..] social media",[106] and also described themselves as "Irish National Socialists".