Tesco will go head-to-head with Apple's iTunes as the supermarket giant launches its own music download service today.

Already a top three UK music retailer from CD albums sold in its stores, Tesco is the first major supermarket to attempt to capture a piece of the £25m legal download market.

Tesco is offering single tracks at a flat rate of 79p from a library of 500,000 songs in an attempt to establish themselves in an increasingly crowded market which analysts predict will grow by 20% in the next three years.

Apple's iTunes currently dominates the field with a share of nearly 70% and many companies including Microsoft, BT and Coca Cola all have their own download services.

Tesco hope to entice customers with promises of superior sound quality and its use of the Window Media Audio format which allows their songs to be used on more than 70 different players.

Gareth Sutcliffe, senior business manager of the Windows Digital Media Division, said: "Music fans want to be able to enjoy the tracks they download anytime, anywhere.

"Because Tesco.com is using the Windows Media Audio format, its customers can choose from a huge range of portable music players."