Around 15,000 suspected pirates may soon get legal letters accusing them of illegally sharing movies and games.
ACS:Law plans to send notes to the accused in the new year offering a chance to settle out of court for “several hundreds of pounds”.
A lawyer who has defended people who have received similar letters described it as a “scattergun approach” that would catch “innocent people”.
ACS:Law said it was “unaware” of anyone who had been wrongly sent a letter.
Andrew Crossley of the firm told BBC News it was acting to “eradicate” sharing of its client’s products.
“We give them opportunity to enter into compromise right at the start to avoid having to deal with it [in court],” said Mr Crossley.
If it went to court and the lawyers were successful, he said, damages “would run into several thousands of pounds”.
But consumer group Which? said that it had heard from around 150 consumers who had been “wrongly accused” in similar cases.
“A lot are accused of downloading pornography,” Jaclyn Clarabut of Which? told BBC News. “People find it distressing or embarrassing and pay up.”
Others, she said, “don’t want the threat of court action” hanging over them or cannot afford to pay for a lawyer and settle the claim for the lower figure.
She said that based on previous experience, “a lot of people will be surprised” by the latest wave of letters.
Michael Coyle, lawyer at Southampton based firm Lawdit, described the scheme as “having very little to do with protecting the rights of the copyright holder”.
Instead, he said, it was “more to do with making money from alleging copyright infringements on a massive scale”.
He has represented several hundred clients who have received letters from ACS: Law and other firms. None of his clients has ever been forced by a court to pay a fine, he said, although some clients had decided to settle out of court.