VoIP services that allow users to make calls to normal national phone numbers must also have the ability to connect to emergency numbers 999 and 112 from 8 September 2008.

Ofcom wants to ensure that users who have switched to VoIP services from traditional landline or cellular phone companies can still access the relevant people in emergencies.

The watchdog expressed concern that consumers needing to locate an ordinary landline or mobile phone in an emergency might face a delay of seconds or even minutes in getting through.

"As new voice services develop and become more mainstream, regulation must evolve too," said chief executive Ed Richards.

"Consumers must be confident that, if they can make calls to ordinary national numbers using their VoIP service, they will be able to call 999 or 112 in an emergency."

Ofcom found that 78 per cent of VoIP users who cannot currently call 999 or 112 either believed that an emergency call was possible, or did not know whether or not this was the case.

The ruling attempts to protect consumers amid increasing use of VoIP services and the trend to look and feel more like traditional fixed and mobile phone services.

Some commentators have voiced concerns over a reliance on VoIP technology, following the Skype outage earlier this year.