Music streaming giant Spotify is cracking down on users who employ apps to bypass restrictions and access a modified version of its premium services without paying.

The Swedish company, which last week filed for a public listing with the US Securities and Exchange Commission, has begun emailing listeners it believes to be using illegal software saying it has "detected abnormal activity" and warning that their accounts have been deactivated and will not be restored until the offending programmes have been uninstalled.

"If we detect repeated use of unauthorised apps in violation of our terms, we reserve all rights including suspending or terminating your account," non-paying subscribers are cautioned.

The free version of Spotify has 88m subscribers but inserts audio adverts every three tracks and ensures songs can only be played on shuffle mode, conditions the premium service removes at a cost of £9.99 a month.

The apps in question do not provide the high-quality streaming a premium account would offer but do allow users to sidestep the adverts and restrictions that many find annoying.

Spotify, founded by Daniel Ek and Martin Lorentzon in 2006, has 159m accounts in total, 78m of which are premium clients.

It said in its recent filing ahead of the stock market floatation that it is optimistic its business will remain lucrative as the public increasingly turns away from paying to own recorded music in favour of buying a subscription fee to access it.

The company recently agreed new licensing deals with Warner, Universal and Sony's music labels to shore up its service ahead of the offering.

The Independent