BCA has received a final warning from the authority due to the high number of customer complaints and the "unacceptable length of time" that the company is taking to resolve them.
The authority first expressed its concern to senior management at BCA in September 2004, and since then its chairman, John Bridgeman, has met with BCA's chief executive George Saul.
The authority said that BCA has assured it that it is improving service standards and has promised to provide regular updates about the levels of complaints received and the way in which they have been resolved. BCA could not be reached for comment.
Book clubs operated by BCA include World Books, The History Guild, The Softback Preview, Books for Children and The Military & Aviation Book Society. BCA is owned by German media giant Bertelsmann.
Marketing Direct's June survey of direct mail spending shows the company halved its spend on direct mail to £13.8m over the last year, although BCA's joint head of marketing claimed the cut was closer to 10% than 50%.
The Direct Marketing Authority is an independent body existing to act on complaints against DMA members.
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