Brexiteer

noun2

1. •
   (UK) Someone who supports Brexit, the United Kingdom's exit from the European Union.

   • After Ken Clarke's "Charge of Light Brigade" hit on Brexiteers in @Daily_Telegraph, Defra SoS likened to Lord Raglan in #CAP reform debate — 2013
2. •
   (UK) Usually in plural: a holder of any of the posts in the British Cabinet tasked with negotiating the country's exit from the European Union.

   • Completing the Three Brexiteers is Boris Johnson, the UK's new Foreign Secretary. — 2016