THE cost of phoning friends and family could fall as more people make calls using the internet.

Internet-based telephone services — voice over internet protocol (Voip) in industry jargon — are used by millions of people in America but have not caught on in the UK. That may be about to change.

The rapid spread of broadband, which is required to use internet telephony, means that more people can access these services. More than 6m households have broadband, with another 50,000 signing up every week.

BT said: “There has been a dramatic growth in consumers’ interest in Voip services. We predict that these services will become increasingly mainstream.”

As the potential market grows, competition between providers is increasing. There are now more than a dozen companies providing web-based telephony, which is becoming steadily more sophisticated.

With most, you download software that converts your computer into a telephone. Then all you need is a microphone and speakers, or a headset that you plug into your PC.

Other operators, such as Sipgate and Vonage, allow you to plug your existing telephone into an adaptor that connects to your broadband modem.

Blair Wadman at Uswitch, a comparison website, said: “As internet telephony becomes part of the mainstream over the next year or so, it will get cheaper because providers will have to battle for business.”

Savings from switching to an internet service can already be substantial. You have most to gain if you make overseas calls or use your phone a lot to talk to family and friends in the UK.

Some calls, such as those to users of the same service, are free, so you can talk at length for no charge other than the broadband line rental.

Jessica Silcox, a 22-year-old student from Leeds, West Yorkshire, saves by using BT’s Communicator web service.

She said: “Because all my family are signed up to the service, calls between us are free. I can now chat to my mum for hours without a huge bill.”

There are obvious drawbacks. Both of you have to be at a computer with a switched-on broadband connection.

But most deals let you call regular or mobile phones in the UK and abroad as well. There is usually a fee for this, although it is often cheaper than with a fixed-line service.

BT’s Communicator package is one of the most expensive. A daytime call to a regular UK phone costs 3p a minute. With Sipgate’s 1000 plan you can call anywhere in the UK for 0.59p per minute, while with Call 1899 and Vonage, UK fixed-line calls are free.

Calls to UK mobiles are more expensive, typically ranging from 5p to 20p a minute.

Huge savings can be made on overseas calls. To phone abroad using BT’s fixed-line service costs at least 5p a minute — £3 an hour. Pipecall’s international call plan, which costs £14.99 a month, offers free calls to 122 destinations, including Australia, France and America.

Gossiptel’s £9.99-a-month World 500 plan offers 500 minutes of free calls a month to 35 destinations.

You can also cut costs for people who call you from overseas. Some operators can give you a telephone number from a specific area. even though you do not live there.

Say your mother lives in Florida and her dialling code is 561. Vonage could provide you with a virtual phone number in dialling code 561 that rings to your UK line. When your mum phones you it costs her the price of a local call.

Some plans, such as those offered by Pipecall and Vonage, charge a monthly fee and set-up costs. BT charges only a monthly fee and others such as Sipgate, Skype and Call 1899 simply charge for calls. Most cannot be used to phone the emergency services.