The client is currently drawing up a shortlist with the help of the AAR and expects to make an appointment by summer 2009.
While the review is being conducted the retailer, which has been advertising heavily on TV and in the national press over Christmas has appointed Rapier to a strategic project.
Rapier's contract will initially last six months and according to a spokeswoman may be connected to B&Q's recently started sponsorship of Channel 4's property programming, including 'Location, Location, Location' and 'Grand Designs'.
JWT has held the account since WPP Group bought B&Q's previous incumbent agency, Bates, in 2003.
Warren Scarr, director of brand advertising at B&Q, said: "As everyone is well aware, the retail marketplace is extremely competitive, and we owe it to our staff and shareholders to ensure that we are working with an agency that best meets our needs in both the current environment, and the longer term."
The review follows the departure just before Christmas of B&Q marketing and customer proposition director Jo Kenrick after three years, as reported by Marketing.
B&Q spent £40m on advertising in the 12 months to September 2008, according to Nielsen.
Its relationship with media agencies ZenithOptimedia and Mediaedge:cia is unaffected by the review.