Mystery shoppers are independent contractors hired to evaluate a business anonymously, said John Swinburn, executive director of the Mystery Shopping Providers Association.

The controversy involves becoming an ''MSPA certified mystery shopper.'' For $115, anyone, from the interested to the professional, can attend an eight-hour seminar and become certified.

But some experienced shoppers say they are unhappy about the one-time certification because companies are giving priority in hiring to certified shoppers. Some shoppers reportedly cannot afford to pay for the certification and lose work for not being certified.

Some experienced mystery shoppers have posted negative statements about certification on http://www.Volition.com, a Web site that serves the mystery shopping community.

The certification seminars have not made any money, said Lorri Kern, board member of the MSPA and president of Kern Scheduling Services, which books mystery shoppers for jobs. Instead, the MSPA has ''lost a ton of money'' on the workshops.

The certification was created in response to Internet hoaxes that promised aspiring mystery shoppers high salaries, Kern said.

''We are trying to legitimize the field,'' she said.

Kern said she doesn't require certification, but reports done by certified shoppers are of higher quality.

She added that she will hire uncertified people if they have worked with her previously.

Kern said she receives 200 requests a day from people interested in mystery shopping.

The MSPA is a trade organization started in 1998 and has nearly 200 members worldwide.