Oftel, the telecommunications industry regulator, estimates it will cost pounds 500m to introduce the scheme and extra time is needed to cope with the changeover.
The Telecommunications Managers Association claims that in total the change will cost billions of pounds.
The new scheme will mean that alarms, faxes and other machines programmed with telephone numbers will have to be reprogrammed. Companies will also have to repaint signs and vehicles. Oftel's estimate excludes the cost to companies of changing numbers on stationery.
Under the plan telephone numbers will have an extra digit added after the first zero, which sends callers into the trunk network. For most users on the fixed network this will be a '1'. Other digits will be used for mobile services such as cellular radio.
The scheme will increase the available numbers tenfold. However, because of the delay Oftel may have to phase it in to help towns and cities where the numbers are running out most quickly. These include Bristol, Bath, Leeds, Sheffield and Nottingham.
The TMA has argued that a simpler and cheaper way of expanding the available numbers is to reactivate unused numbers.
The problem is that while a billion national numbers are available theoretically only 650 million can be used. This is partly because the current system earmarks blocks of numbers for exchanges in specific areas. If the numbers are not needed in an area they cannot be moved around to fill gaps elsewhere.
The boom in the use of facsimile machines and special premium rate telephone services adds to the concern. But one of the main problems is that, as more competition emerges in the form of mobile telephone services and cable television firms offering telephony, the greater the demand for numbers will be.
The Telcommunications Users Association fears too long a delay could prove disatrous. Vivienne Peters, director of the association, said: 'I am concerned that we are rapidly running out of numbers in some areas of the country. There is also a real threat to new competition coming into the market if potential rivals to BT are uncertain about the future numbering scheme.'Reuse content