America's Scouting movement is fighting to keep secret thousands of "perversion files" on suspected child molesters after it was ordered to pay record damages over the sexual abuse of a former Scout.

In a growing scandal threatening to rival the crisis hitting the Roman Catholic church, the Boy Scouts of America has been accused of covering up decades of child abuse in order to protect the reputation of what is now a billion-dollar organisation.

Last week, a jury in Oregon made the largest punitive damages award to a single plaintiff in a child abuse case in the US by ordering the Scouts to pay $18.5m (£12m) to Kerry Lewis, who was repeatedly assaulted by a former assistant scoutmaster, Timur Dykes, in the 1980s. Dykes had admitted to a superior in the Scouts that he had abused boys, but was allowed to remain in the organisation and is alleged to have sexually assaulted several other children who are also taking legal action.

The judge in the case overruled the Scouts' attempts to keep the jury from seeing about 1,200 files kept by the organisation on suspected paedophiles. Kelly Clark, Lewis's lawyer, told the jury that while the files were often used to remove child abusers from the Scouting movement, many were allowed to remain in the organisation. He said that the Scouts rarely alerted the police and when they did, the movement asked the authorities to avoid publicity.

Clark told the jury that the Scouting leadership had been "reckless and outrageous" in failing to warn parents and boys about the problem.

The files shown to the jury were not made public and are just a small part of what is believed to be a cache of as many as 6,000 held at the Scouts' headquarters in Texas, dating back to the 1920s. Lawyers for alleged sexual abuse victims are suing to have all the files made public at a hearing next month.

If that happens, it is likely to prove a severe blow to an organisation that is already at the centre of controversy over a bar on atheists and gay people. Membership stands at about 3 million, but has been dropping for more than a decade, in part because of the controversies over discrimination.

Clark said the scale of the award to Lewis reflects a heightened awareness of sexual crimes against children because of the recent revelations about the Catholic church. But he also said that the jury was shocked by the existence of what in court were called the "perversion files".

"We said they had 75 years of secret files about paedophiles, and that's the way the evidence came in. I think that fact in itself was just staggering to the jury," he said. "They had a regular practice of placing guys on probation and then they would allow them to continue to be active in Scouting, not unlike some of what you saw in the Catholic church."

Dykes confessed his abuse in 1983 to the local Scouts co-ordinator, who also happened to be a Mormon bishop, but was allowed to continue working with the Scouts. Lewis said he was molested by Dykes over the following two years. The Mormon church settled with Lewis and seven other victims of Dykes more than a year ago.

Clark said the Scouts shared information from the files when requested to do so by the police, but it almost never took the initiative in submitting a case to the authorities, even where there was credible evidence of abuse.

"The routine was that they would deal with it internally," said Clark. "They would place the paedophile on their list of ineligible volunteers and if it was dropable they would drop it, and it was done. There were numerous examples of Scouting executives saying 'let's keep this quiet, he's out of Scouting now, so we don't need to do any more about it.' There was definitely a misguided sense of priorities."

Even where the police did become involved, the Scouts sought to minimise the damage to the organisation.

"We saw numerous examples of the Scouts writing to law enforcement saying 'it would be best for the good of Scouting if this could avoid being made too public.' Law enforcement was almost complicit in this saying 'we'll do our best to keep this quiet because we value the work of the Boy Scouts,'" said Clark.

The Scout leadership said it was seeking to keep the files secret to protect the privacy of the victims and to guard against being sued for false accusations. It said it was "deeply saddened" by the abuse of Lewis, but would not comment further on the case because of continuing litigation.

"The Boy Scouts of America has a rigorous, nationwide system of checks and balances, in accordance with local laws, which keeps out of the programme those individuals who should not be leading youth," it said.

But Patrick Boyle, author of Scout's Honour: Sexual Abuse in America's Most Trusted Institution, said the Scout leadership lost sight of its real purpose in dealing with paedophiles.

"They've behaved like a corporation with an embarrassing product defect that they don't want to acknowledge. The Scouts were minimising the extent of the problem within their organisation and in large part discrediting their own Boy Scout victims and trying to hide the product defect, so to speak, by not letting on how many cases they have, misleading people into thinking they didn't really know how many cases they have, they didn't have a file system. And then fighting tooth and nail in court to keep it secret," he said. "They have also been very heavy handed with the victims, not apologising."

Scouts' dishonour

The Boy Scouts of America organisation has been at the centre of nearly three decades of controversy ranging from out-of-court settlements with victims of childhood sexual abuse to its bar on non-believers and gay people.

Although Kerry Lewis won the largest punitive damages to date ($18.5m) awarded over sexual molestation, the Scouts in the US have settled about 60 similar cases out of court over recent years.

Until last week's judgment, the Texas-based Scout movement had previously fought off several court actions, including an attempt to overturn its policy that atheists and agnostics who were not prepared to swear allegiance to God could not join. It also beat off legal attempts to force it to drop an effective bar on openly gay members on the grounds that being homosexual is not consistent with the organisation's requirement to be "morally straight". The Girl Scouts of America, a separate organisation, permits members to submit a word other than God when reciting its oath and has no restrictions based on sexual orientation.

Some critics have accused the Boy Scouts of losing touch with its original purpose as it has evolved into a an organisation which in some ways resembles a large corporation, with close to $900m in assets, including a $45m art collection and a large property portfolio.