Fox joined the Revolutionary Communist Party as a student at the University of Warwick. For the next twenty years, she was one of the RCP's core activists and organisers. She became co-publisher of its magazine Living Marxism, which closed in 2000 after the courts found it had falsely accusedIndependent Television News of faking evidence of the Bosnian genocide. In 2018, Fox refused to apologise for suggesting evidence of the genocide was faked. Fox stayed with her ex-RCP members when the group transformed itself in the early 2000s into a network around the web magazine Spiked Online and the Institute of Ideas, both based in the former RCP offices and both promoting libertarianism. Author and environmental activist George Monbiot has argued these groups are part of the "pro-corporate libertarian right".
Media career
Fox has been a guest panellist on BBC Radio 4's programme The Moral Maze, and appeared as a panellist on BBC One's political television programmeQuestion Time. Fox has been criticised in The Guardian for rejecting multiculturalism as divisive and her libertarian belief in the desirability of minimal governmental control and support of free speech in all contexts. She has been accused of "supporting Gary Glitter's right to download child porn", something of which she says "I feel stupid for saying paedophilia is disgusting". In 2015, she was listed as one of BBC's 100 Women. Fox wrote the book I Find That Offensive! in 2016.
Brexit Party
In April 2019, Fox became a registered supporter of the Brexit Party. She was in the first position in the list for the Brexit Party in the North West England constituency at the 2019 European Parliament election. The candidacy was announced on 23 April 2019. Fox's selection was criticised by the father of murdered schoolboy Tim Parry for her past support for the Provisional Irish Republican Army and the RCP's defence of the 1993 IRA Warrington bombings, which had killed his son within the North West England constituency. Another candidate for the Brexit Party, Sally Bate, resigned, citing Fox's "ambiguous position" about IRA violence. A Brexit Party spokesperson commented on the criticism of Fox: "It's a desperate attempt to cause trouble". Fox was subsequently elected to serve in the European Parliament. She remained in this role until the United Kingdom's withdrawal from the EU on 31 January 2020.
In 2020, Fox was nominated for a peerage and will sit as a non-affiliated peer, despite her claiming to be against the existence of the House of Lords.