The agency has worked on the brand since the middle of 1999, and last faced a review of the account in October 2003.
This reappointment comes as Kia reviews its 拢60m European media account. Last week, incumbent agency Starcom Motive said it was withdrawing from the review.
Mustoes' most recent work for the brand positions its Picante model as the "thinking person's small car". Kia said that the success of the ad had contributed to the reappointment.
Paul Williams, UK managing director of Kia, said: "We're delighted with the strategic and creative work being produced by Mustoes.
"It's not easy creating the fastest growing car manufacturer in the UK, but the advertising helped achieve this, with a 27% increase in Picanto sales and a 229% increase in footfall into dealerships since the campaign launch."
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