The agency will look to create local media coverage, partnerships and city-based activities in the new locations: Birmingham, Edinburgh, Glasgow, Leeds, Liverpool and Manchester.
London-based agency Rebecca Abigail PR will continue to handle the brand's national and London PR.
Chris Lamontagne, head of growth at GetTaxi, said: "The Muckle team is nimble and creative, which is what made it the perfect launch partner as we grow across the UK."
