The move is expected to spur on more households to swap between competing companies in a bid to get a better deal by removing the hassle of having to change numbers. The agreement covers the major telephone companies who will have terms written into their licences obliging them to let customers keep their numbers if they defect to rival companies.
Until now, only BT has been obliged to let customers keep their numbers. Since June last year more than 150,000 telephone numbers have been switched between companies - now running at around 5,000 a week.
Don Cruickshank, director general of the industry regulator Oftel, said there was clearly demand for "number portability" and said that today's move was good news for telephone users.
Mr Cruickshank said: "Now customers can move between any operator to ensure they are getting the best quality of service at the best price - without the inconvenience of having to change numbers.
"The fact that customers had to change their numbers when moving between operators was a big obstacle to competition."
Some companies have been offering portability until now on a voluntary basis.
Moves are also under way to let customers keep their mobile telephone numbers or numbers for special-rate services such as freephone and local- rate calls if they move between companies.Reuse content