The business has been with EHS Brann since 2001, when the car relaunched with a basic version, a Mini Cooper and a Mini Cooper S. Earlier this year it added a Cabriolet.
The review, which is being handled by the AAR, is part of a statutory process, according to a spokeswoman for Mini. The above-the-line business, held by WCRS, is unaffected.
The decision to review the account reflects a change in strategy. Mini will set up a CRM programme, aimed at building a relationship with its large customer database, using data from its website.
EHS has also worked on substantial digital activity, including the creation of a website, www.mini.com.
The Mini website enables prospective customers to choose which model they would like to buy and to personalise their cars.