Her decision is thought to have been sparked by differences over the business's strategy. Smith is now on three month's gardening leave.
The move will come as a shock to the industry as Smith has built The Prospect Shop from a start-up in the list industry to a data managment firm and broker with a turnover of more than 拢3m in just three-and-a-half years.
It is not thought that Smith's role at the DMA, where she is said to be highly valued, will be affected by her decision as she will continue in her role as a principle of data consortium Business Suppression, also a DMA member.
"[My role] is in the gift of the [DMA] board," Smith said. "That will be until the board is re-elected."
The DMA board is meeting at 10am today and an official announcement is expected as to whether she will continue there.
Jenny Moseley, chairman of the DMA, said: "Rosemary is so valuable in her role as chair of governance and in her work with compliance issues. There is no doubt in my mind that the DMA board will ask her to stay."
Smith refused to be drawn on what her next plans will be. However, sources close to her have indicated that she is planning to stay in the industry and it is thought likely that she will set up as an independent list broker and manager.
Smith has worked at The Prospect Shop since 1999 when the company was a joint venture between German list company Schober and Swedish media firm Bonnier, which was behind Business a.m. and the European versions of the Metro free newspaper.
In 2000, the venture -- then called Schober -- was bought out by Bonnier, and Smith oversaw the development of the business into what it is today, one of the UK's top 10 list companies offering its own data as well as brokering and management services.
Smith's career in data began when she took up the post of director of membership services at the Periodical Publisher's Association, with responsibility for data protection.
In 1989, she joined Reed-owned list firm Mardev as research director and rose to the post of managing director. The company was then sold to Acxiom in 1996 and Smith remained there until 1999 running its data management and call centre business.
Smith is also a personal investor in Business Suppression, alongside its other members including The Prospect Shop parent Bonnier. The consortium's other backers are Developing Data, Mardev, QBase and e-crm.
Bonnier has appointed Hugh Bessant, a senior executive of the Swedish firm, as managing director of The Prospect Shop with immediate effect.
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