Morgan Stanley Dean Witter, the US financial services company, is reviewing its direct marketing account, held by WWAV Rapp Collins.
Agency sources reveal that the account, which involves mass mailings to support Morgan Stanley's credit card, will be worth more than pounds 20 million.
One source said Morgan Stanley will ask for credentials from nine agencies and draw up a shortlist of four.
Mark Mayhew, the UK country manager at Morgan Stanley, said: 'We are taking a look at some aspects of our direct marketing. WWAV is our agency of record but we are looking at things as we grow our business.'
Leo Burnett and Starcom Motive, which handle creative and media for the card, will not be affected.