By Jane Wakefield
Technology reporter, BBC News
No cases have yet gone to court
Music industry representative the BPI has criticised the approach used by a UK law firm in chasing file-sharers.
Law firm ACS:Law has sent thousands of letters to people it claims have downloaded illegal content.
The BPI said it did not condone the approach of mass-mailing alleged internet pirates.
A law firm that represents some of those sent letters has called on the Information Commissioner to investigate the matter.
The BPI said it would not be adopting the same approach as ACS: Law if UK legislation on the issue of illegal file-sharing comes into force.
"We don't favour the approach taken by ACS:Law to tackle illegal file-sharing," said spokesman Adam Liversage.
"Our view is that legal action is best reserved for the most persistent or serious offenders - rather than widely used as a first response," he added.
The government Digital Economy Bill is in the process of going through parliament.
In it the government lays out its approach to the issue of illegal file-sharing which would start with sending letters to those addresses linked to computers found to have been downloading illegal material.
Some of the accused could have had their network hacked into
If a letter campaign does not work, more drastic action, such as removing them from the network, will be taken.
Consumer publication Which has been approached by 150 people who have received letters from ACS:Law and say they are completely innocent.
It highlights one of the problems with the software used to track file-sharers, namely that finding an IP address of a computer does not necessarily find the person who has committed the crime.
It could be that someone else has used an unsecured wireless network, effectively piggybacking on a householder's network to download illegal content without being traced.
Or, in other cases, it could be that another member of the household is responsible.
ACS:Law said that it is happy that the methods used to trace file-sharers is completely accurate.
But lawyer Michael Coyle from Lawdit, who represents around 100 people who have received letters, is concerned that none of the cases has gone to court.
"About 10% of them have paid but the rest have just disappeared," he said.
He is not convinced that the evidence would stand up if they did go to court.
"It seems to me that the only way that a claim can be upheld is if you admit the claim or they inspect your hard drive," he said.
Andrew Crossley from ACS:Law told BBC News that cases are pending.
"It has been said that we have no intention of going to court but we have no fear of it," he said.
He represents a range of clients, including German firm DigiProtect.
DigiProtect is not a content company itself but agrees with rights holders to pursue file-sharers on their behalf.
Mr Coyle said that there are other firms "jumping on the bandwagon".
One of his clients was contacted on behalf of an English firm called MediaCat whose members include two London-based pornography companies.
Mr Coyle said that his client was accused of downloading 22 adult films and ACS was "demanding £11,000".
"The whole thing is now so bizarre that I don't actually think it's got anything to do with copyright any more," he added.
Mr Crossley said that MediaCat seeks "£540 per infringement".
"It is an appropriate settlement and if it went to court the claim would be for £3,000 per infringement," he said.
He said his client did not pursue people "who have just downloaded something".
"The system is designed to monitor uploads not downloads."
"It is the equivalent of someone stood outside HMV with a pile of the latest albums, handing them out to people who were intending to go in the shop and buy it,"
But Mr Coyle questions the motives of firms such as MediaCat.
"We have been approached by similar companies in Belgium and Germany asking us to do the same sort of thing. To me it seems like a license to print money, all you have to do is hold your nerve, beat the stick and most people do pay," he added.
He thinks the practice needs to be stopped.
"I suspect that many hundreds of people have been innocently accused of copyright infringement and the accusations continue without any organisation being prepared to intervene," he said.
"Ideally the Information Commissioner ought to intervene and seek to prevent the courts releasing the personal data of thousands of individuals," he added.