The regulator said some operators still sold devices which can not be used on other networks unless they are unlocked for a fee.
It said its own research had found the issue was dissuading some people from switching and so was proposing the ban to allow easier movement between networks.
It follows reforms introduced in July which now allow people to start the process of moving network by sending a single, free text message.
Currently, people switching between providers on Openreach's copper network - such as BT, Sky and TalkTalk - have a relatively simple process, but Ofcom says switching to a different network, such as CityFibre or Virgin Media, requires coordinating the change with both their existing and new provider.
The proposals are designed to reflect new European rules currently coming into force on the subject.
Lindsey Fussell, Ofcom consumer group director, said: "Switching mobile provider can be really frustrating.
"By freeing mobile users from locked handsets, our plans would save people time, effort and money - and help them unlock a better deal."
The proposals have been welcomed by industry experts.
Richard Neudegg, head of regulation at uSwitch.com, said: "This latest round of Ofcom proposals on selling unlocked handsets is great news for consumers.
"Smartphones can cost in excess of £1,000, so expecting people to fork out that sum of cash for a restricted device feels incredibly outdated.
"Changing network is getting easier and easier thanks to rules such as text-to-switch and the introduction of end-of-contract notifications coming in February next year.
"We also welcome Ofcom's plans to improve the experience of switching broadband providers. As more new fibre networks start offering services to consumers, it's vital that switching processes keep up with the increased choice.
"Ensuring that switches are always done automatically, and are smoothly coordinated by the new company, will help ensure that people are not put off moving to better services.
"However, the devil is in the detail and we need to see exactly how industry translates these proposed new principles into a switching system that really works for consumers.