The government has set a secret target to reduce illegal filesharing of music and films by up to 80% over the next three years, MediaGuardian.co.uk can reveal.

The goal was outlined in a letter by Baroness Vadera, the business minister, relating to the agreement the government struck with internet service providers and the film and music industries to curb illegal filesharing.

The leaked letter, dated July 22, was sent to all the proposed signatories of the memorandum of understanding which proposes to "significantly reduce" illegal filesharing in the next two to three years.

"Although this letter has no effect on the agreement, which stands in its own terms, this may help to ensure all signatories have the same expectations," Vadera wrote.

"I would regard a reduction as 'significant' if it had reduced the number of people filesharing unlawfully in the UK by well over 50%, and we hope in the region of 70%-80% from a baseline to be agreed, with work to start immediately, rather than waiting for legislation."

But Vadera's target did not form part of the memorandum of understanding, released yesterday and other parties to the agreement have not signed up to it.

Industry estimates put the number of illegal filesharers in the UK at between 6 and 7 million people.

"Success will significantly depend on the effectiveness of the letter writing, awareness raising and other measures," Vadera adds.

Part of the memorandum requires the UK's six biggest ISPs - BSkyB, Tiscali, BT, Orange, Virgin Media and Carphone Warehouse - to send out 1,000 letters a week to subscribers identified as having engaged in illegal uploading or downloading of music.

Following the three-month trial, media regulator Ofcom will agree an "escalation" in the number of letters and broaden the campaign to target other content being illegally shared, such as films.

Ofcom will look to use other measures to deal with repeat offenders, including slowing internet speeds or blocking content. Rights holders will consider prosecuting "particularly serious infringers".

Some analysts are sceptical that the government's goal can be achieved without heavy measures being introduced.

"I think trimming off a million filesharers from the total number in the UK would be a great measure of success for this letter campaign, but even that would be an unprecedented success in tackling global file sharing," said Mark Mulligan, a vice-president at analysts Jupiter Research.

"In the US, where the Recording Industry Association of America has been very aggressive, the result has predominately been one of containment."

The BPI, the body that represents record labels, is keen on a three-step procedure to tackle illegal filesharers.

First, an "educational" letter would be sent to customers explaining the account abuse. If a customer was identified a second time, their account would be suspended until an undertaking promising no more illegal use was signed. A third breach would result in cancellation of their internet account.

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