First came the Digital Economy Act, and now only weeks into its existence a suggested add-on that would transform a controversial law into a ridiculous and unfair content tax.

The UK Performing Rights Society (PRS) for Music wants ISPs to be compelled to pay out according to the volume of pirated music that pass across their networks.

The first problem is how to measure such a thing and for that the PRS suggests Detica's Cview, a file sharing measurement tool that has been in trial with ISP Virgin Media since its launch last year.

One service provider, Interoute, claims this would cost the industry between £30 million to £50 million to raise for the music rights holders to gain something around £200 million. This, says Interoute (and no doubt many ISPs are thinking the same), is an unfair cost to impose on one industry in order to protect another.

More to the point, if such an amendment came to fruition, the effect would hit the bottom lines of ISPs, at which point they would pass the bill - for the rights compensation and the measurement system costs - on to customers.

The proportion of customers abusing music content from file-sharing networks is tiny in relation to the customer base as a whole but the average honest consumer would inevitably end up paying for all of this in higher subscription fees.

Bear in mind that there would be no alternative but to pass on the costs to everyone. Detica went out of its way to stress that its system is no Phorm-by-the-back-door. It cannot relate IP addresses to content downloaded. It makes only overall measurements of activity and can't surgically pick on the worst offenders. The DEA was meant to do that, ironically.

The music rights holders would be very pleased with themselves at which point other rights holders for TV, video, books, you name it, would move in for their own cut. This is nothing less than a sneaky tax on behalf of one interest group made on another, the consumer, the overwhelming majority of whom have never heard of eDonkey or Torrenting.

They will no doubt claim that piracy would reduce if such costs appeared on people's bills but this seems unlikely. Burglary doesn't get less frequent because insurance companies charges larger policy excesses. More probably, copyright thieves would find new ways to hide themselves leaving everyone else to pick up the tab.