The Federation of Small Businesses is offering its 210,000 members a voice over IP service enabling them to communicate with each other for free.
The deal, through Coms PLC, will provide FSB members with a business-class VoIP telephony service via Redstone company FSB Telecom.
FSB members will receive a VoIP telecoms account, through which they can contact each other free of charge.
They can sign up for the service in the members section of the FSB website, or by going to a special site.
Members can log onto the website using their membership details, and are given an individual VoIP telephone number which is then included within the FSB members directory.
Sandy Harris, the Federation's director of member services, said, "FSB VoIP will be a valuable addition to the business networking opportunities available to our members through our online directory."
Members will be able to upgrade their account to a full VoIP account, which will give them an additional line with no installation or monthly costs.
They will only pay for calls outside the FSB members' directory.
Terry Martin, chief executive of Coms PLC, said, "This is further evidence that hosted VoIP has come of age."