"The Prime Minister did not advocate banning encryption; he expressed concern that many companies are building end-to-end encrypted applications and services and not retaining the keys."
We will not ban encryption.
We will not require encrypted communication applications to include a copy of the key they use encrypted with a key that the GCHQ can read with every message.
But we will require that the company who sold you the encrypted communication application either generate all the keys, and keep copies of them, so we can come around and ask for them.
There's a difference? Well, in the first two cases, the government can read everything; in the third case, they'd actually have to get a court order or something, and even in the case of the intelligence services, it would be awkward to read everything. Unless they tapped the lines of the software company.