Spotify, the Swedish internet radio station that allows users to stream tracks over the internet, is improving sound quality for 'Premium' users.

Spotify is free to use, although listeners will find tracks peppered with adverts, just like commercial radio. However, for a £9.99 monthly subscription, users can enjoy ad-free listening.

Now, they'll also be offered an 'enable high bitrate' option in the preferences, which the company says doubles the current streaming quality and offers a sound-quality similar to CDs.

Not all of Spotify's catalogue will be available in high-quality immediately. The music streaming service said initially it will only be available on the most popular tracks such as Lilly Allen's The Fear, with more and more tracks being converted over the coming weeks.

"Providing great sound quality has always been an important goal for us. Now, we're taking the next step in offering an unparalleled listening experience, Spotify chief executive Daniel Elk said.

The company said the free service will continue to be streamed at the standard rate for the foreseeable feature.

The upgrade will effectively double the current quality offered to users, with Spotify now claiming to provide the highest streaming rate for any digital music service.