Hundreds of men who say they were wrongly accused of child pornography offences could have their names cleared after a case to be heard in the court of appeal tomorrow.

One of the 3,700 men arrested as part of Operation Ore in 2002, who says his life was ruined after he was falsely associated with one of the UK's biggest online child-abuse rings, will argue that his credit card details were stolen and used on paedophile sites.

The case stems from Operation Ore, an unprecedented police investigation that led to the arrest of 3,700 men in 2002 after they were linked to an American US-based website, "Landslide.

Police and prosecutors claimed that the men had all clicked on a banner advert on the site, which read: "Click here for child porn," and that police had obtained the names and addresses of more than 7,000 UK users who had followed the link.

But the lawyer acting for the man mentioned said that many of the suspects were innocent.

"Criminal webmasters would use stolen credit card details or take them from their own legal adult pornography sites and re-enter them to sign up for subscriptions to their illegal sites for child pornography," said Chris Saltrese. "There is evidence of bundles of different cards all being entered from one place, one after the other. It was simple fraud."

The appeal court will also hear that the banner was only ever one of a series of rotating ads that led to a legal adult pornography site.

Operation Ore has attracted controversy in the UK for the number of suspects it targeted. Critics claim that, whereas in the US, details were available of 35,000 users of the site but only 100 were prosecuted, the UK authorities prosecuted 1,800.

Thirty-nine of the men are reported to have killed themselves as a result of being prosecuted during the Ore inquiry, and campaigners say many others pleaded guilty to avoid the publicity of a trial.

The case, which has been strongly contested by officers involved in the original investigation, comes amid continuing controversy over efforts to target child exploitation online in the UK.

In July the government announced that CEOP, the Child Exploitation and Online Protection Centre, which is responsible for prosecuting offenders, would be absorbed into the National Crime Agency, following the coalition's programmme Policing in the 21st Century, announced in June.

Senior politicians close to CEOP have said that absorbing the organisation into the National Crime Agency will put children at risk.

"CEOP's effectiveness will be lost," a senior source said. "Effective child protection relies on knowledge running throughout an agency. It will be difficult to develop this in a large organisation like the National Crime Agency."

Last month head of CEOP Jim Gamble resigned, four months earlier than his expected departure, in protest at the plans, four months earlier than his expected departure, and has been placed on gardening leave. A number of other senior managers in the organisation are also thought to have resigned.

Although Operation Ore was conducted by the National Criminal Intelligence Service, a forerunner of CEOP, the investigation has attracted criticism for the organisation, as today's appeal could pave the way for other men to have their convictions overturned.

"I have clients who have lost everything: their jobs, their homes, their marriages, their children and their health," Saltrese said.