Ofcom, the communications watchdog, which has already cut the time it takes to transfer a mobile phone number from five days to two days, hopes speeding up the process will encourage more consumers to switch providers in order to get better deals.

Ed Richards, chief executive of Ofcom, said: “We would like to see easier, faster and more convenient processes to enable consumers to keep their number when they switch mobile provider.”

Ofcom said the new arrangement, which should come into force in 2011, would make Britain the fastest country for number “porting” in Europe.

The watchdog first proposed the change in 2007, but the plans were scuppered last year when the Competition Appeals Tribunal (CAT) ruled that Ofcom had failed to prove that speeding up the process would cost operators only £5m.

The UK’s larger operators, led by Vodafone, had argued that the process would cost “significantly more”.

A spokesman for Vodafone said: “Our goal is a system that’s convenient, works reliably and lets customers make informed decisions without compromising vital consumer safeguards against slamming, mis-selling and fraud.

“We are always open to ideas for genuine improvements, but they must give real customer benefits at a proportionate cost.”

Ofcom is also proposing changes to rules which force the customer to contact their provider to request a “PAC code” before they can switch to a new network.

In most European countries the network the customer wants to move to (known as the recipient) arranges the number transfer.

Ofcom said its research showed most British consumers would prefer British operators adopted the same practice.

Matt Hatton, analyst at Analysys Mason, said: “A change to a recipient-led process may make it easier for consumers to switch providers, but it could led to an increase in ‘slamming’, where a customers’ provider is changed without their consent.”