YouTube has agreed to pay royalties for songs used in videos on the site, in a deal that means music publishers will treat it much as they do radio stations.

The video-sharing site struck an agreement with a society that collect royalties on behalf of more than 50,000 composers, song-writers and publishers, meaning that videos using their music as a soundtrack will no longer be infringing copyright.

YouTube will pay a flat fee - the amount of which has not been disclosed - to license more than ten million pieces of music in the "first fully formed agreement" of its kind, according to Steve Porter, chief executive of the royalty-collecting MCPS-PRS Alliance.

The decision about how to divide up the fee, which will be similar to the one paid by radio and television broadcasters, will be based on an estimate of what music has been played on the site, the MCPS-PRS said.

The agreement will go some way towards reassuring content owners, who have been concerned about the amount of material that appears illegally on YouTube and which does not generate any revenue for its creators.

All four major record labels have now made licensing deals which mean they take a share of the advertising revenue when YouTube carries their music, but this is the first deal which ensures that revenue will also be collected on behalf of song-writers and publishers.

Media companies wanting to use songs must typically negotiate separate licensing deals with record labels, which own the copyright in recordings, and publishers, which own copyright in the words and melodies.

The National Music Publishers Association - a similar organisation to the MCPS-PRS in the US - recently joined a class-action lawsuit against YouTube accusing it of copyright infringement.

The MCPS-PRS, which counts among its members the four largest publishers - EMI, Sony/ATV, Universal/BMG, and Warner/Chappell - said it would work with YouTube to improve the technology used to monitor songs used in videos on the site, and that initially it would focus on clips which attract the highest audiences.

"We're more interested in videos that are played three million times rather than three times," Andrew Shaw, the managing director for broadcast and online at the MCPS-PRS, said. "Logic would dictate that you start with the high volume videos and work your way down to the long tail."

The MCPS-PRS deal covers publishers based in the UK and elsewhere, but is only applicable to royalties which stem from clips watched by YouTube users in the UK.

YouTube, which is owned by Google, is undertood to be negotiating similar deals with collecting societies in other territories.