Mobile phone companies are to be banned from selling devices which are "locked" into specific networks, the communications regulator has ruled.
Ofcom said the likes of BT/EE, Tesco Mobile and Vodafone will be told to follow their other big name rivals in only supplying phones which allow customers to switch from one network to another while keeping their existing handset.
The rules will come into effect from December 2021.
Selina Chadha, Ofcom's connectivity director, said: "We know that lots of people can be put off from switching because their handset is locked.
"So we're banning mobile companies from selling locked phones, which will save people time, money and effort - and help them unlock better deals."
Currently, companies such as BT/EE, Tesco Mobile and Vodafone still sell mobile phones which cannot be used on other networks unless they are unlocked.
Customers can unlock their phones, although it costs money to do so.
Ofcom said it expects widespread compliance with the new rules, and companies breaking them risk being slapped with heavy fines.
A Vodafone UK spokesman said: "We stand ready to implement these changes, when they come into force."
Richard Neudegg, head of regulation at comparison site Uswitch.com, said the announcement "will finally rid the industry of this anachronistic practice".
He said: "Despite some modest improvements to the process, unlocking, when required, is often a pain.
"When the new rules come into force, customers will be able to buy the phone and package they want, with whatever network, safe in the knowledge that if they later choose to switch to another network, they can do so easily and base the decision purely on what's right for them."
