An jury in Oregon has ordered the Boy Scouts of America to pay $18.5 million US in punitive damages in a sex abuse lawsuit. It is believed to be the largest award ever granted by a jury in a sex-abuse lawsuit against the organization.

The amount is in addition to $1.4 million US awarded to Kerry Lewis in compensatory damages last week, after the jury found the Scouts were negligent for failing to prevent abuse by an assistant Scoutmaster in the early 1980s.

The punitive damages award on Friday came in the second phase of a month-long trial that centred on files the Scouts have kept on suspected child molesters since the 1920s.

Lawyers for Lewis, 38, argued the organization was reckless for allowing former assistant scoutmaster Timur Dykes to continue to associate with the victim's Scout troop after Dykes acknowledged to a Mormon bishop early in 1983 that he had molested 17 scouts.

The Mormon church was the local affiliate, or "charter" organization, for an estimated one-third to one-half of the Boy Scout troops in the United States in the 1980s. It had already been ordered to pay compensatory damages but was not subject to punitive damages.

The Boy Scouts denied the allegations of negligence and said their files actually helped them keep child molesters out of their ranks.