It is understood that more than 150 people in the UK have been wrongly accused of illegal file-sharing in new crackdowns, and sent threatening letters demanding an out-of-court settlement of £500, according to the BBC.

Consumer publication "Which?" has been approached by over 150 people who say they have no knowledge of the illegal file-sharing of which they have been accused. ACS:Law, the London-based firm behind the letters said its methods were accurate and that more letters would be sent soon.

"My 78 year-old father yesterday received a letter from ACS Law demanding £500 for a porn file he is alleged to have downloaded," one person told Which? "He doesn't even know what file-sharing or BitTorrent is so has certainly not done this himself or given anyone else permission to use his computer to do such a thing."

Matt Bath, technology editor of Which? said "Innocent consumers are being threatened with legal action for copyright infringements they not only haven't committed, but wouldn't know how to commit." He added that many would "be frightened into paying up rather than facing the stress of a court battle."

He advised those wrongly accused to "rigorously deny it and, if possible, provide physical evidence of where they were when the infringement took place." He also said that they should contact Which? about their case.

Andrew Crossley of ACS:Law said that some cases had already been dropped. He also said that the method used to detect the IP address used was "foolproof".

"We are happy that the information we get is completely accurate," he said. "We explain that an infringement has taken place but it may not be the account holder who has done it."

None of the 10,000 actions sent by the firm have yet to go to court, according to Crossley, but the firm apparently has "no fear of it," with some already going to court. He admitted that the majority of people settle out of court.

However, Matt Bath said that he doubts that the firm could prove beyond doubt that any particular individual was responsible for the illegal downloading.

As reported by the BBC, ACS:Law is currently being investigated by the Solicitors Regulation Authority.