Police have arrested eight people over a fraud case in which several companies were deceived by a business directory firm.

About 300 victimised companies have complained to Police since late last year that they received unsolicited letters from a directory firm inviting them to verify and update their company's details for inclusion in a publication similar to the Yellow Pages.

However, the letter also contained small print outlining conditions requiring the companies to pay for subscribing to the advertising service. The paragraph was often unnoticed by the victims until they received invoices from the firm. Forty-one complainants paid more than $540,000 in advertisement or cancellation fees.

Officers arrested three men and five women, aged 19 to 41, including the firm's director, shareholder, general manger, and customer representatives. All have been released on bail pending further investigation.