Britain's six largest internet service providers (ISPs) have agreed to send out letters to customers they suspect of sharing copyrighted music files online.

BT, Sky, Virgin Media, Orange, Tiscali and The Carphone Warehouse have signed a Government 'memorandum of understanding', agreeing to send 'informative letters' to customers accused of sharing copyrighted music files.

Information on who is sharing the files will be provided by music industry body the British Phonographic Industry (BPI), which today described the memorandum as a "significant step forward in tackling illegal file-sharing".

Chief executive Geoff Taylor said: "BPI has always believed that a partnership approach is the best way forward, as we showed with our education campaign with Virgin Media launched in May.

"This has demonstrated that ISPs and the music business can work together positively to raise awareness about illegal file-sharing."

He said the BPI would work with the ISPs to create the procedures "necessary to effectively tackle repeated unlawful file-sharing".

Four of the ISPs involved denied that the agreement marks the beginning of a 'three-strike' system whereby those who continue to share copyrighted music files would have their internet access cut off.

A representative for Orange told Computeractive: "As part of this wider agreement, Orange will continue to work with content owners and alert customers if they are allegedly in breach of any copyright laws.

"However, as has always been Orange's position, we will not disconnect internet accounts for alleged copyright infringement or disclose customer details to content owners without a court order."

Charles Dunstone, CEO of The Carphone Warehouse, agreed: "We will not divulge a customer's details or disconnect them on the say-so of the content industry, but we will work with rights holders to develop a sensible and legal approach founded on protecting consumer rights and privacy."

A BT representative said: "There is no obligation on us to put in place a three-strikes or disconnection process", and a spokesperson for Virgin Media said that "we don't think three strikes is the best approach, but we will comply with any legislation".

However, such a system could be implemented in future. The BPI said it would continue to push for a three-strikes system, which it has described as "the simplest and most effective way that ISPs can voluntarily cooperate with rightholders to tackle illegal file-sharing".

A representative for the organisation told Computeractive: "We've been very clear that the three- strikes system is the best way to deal with repeat offenders, but we will have to speak to Ofcom to determine if this will go ahead."

A representative for Sky said that the company was "in discussions with rights owners about how a notification trial might best deliver insight and inform future frameworks", and that it was "still looking into" a three-strikes system.