FLAGSTAFF, Ariz. — A new report by a federal watchdog outlines a history of harassment on river trips through Grand Canyon National Park in which male park employees allegedly propositioned female colleagues for sex, touched them inappropriately, and made lewd comments.

The report obtained by The Associated Press comes after 13 current and former Grand Canyon employees filed a complaint in September 2014 saying that women had been abused over 15 years. It was released Tuesday by the Department of the Interior’s Office of Inspector General.

About a dozen people have faced disciplinary action for sexual misconduct since 2003, ranging from a written reprimand to termination. But investigators say those actions are inconsistent, and many alleged incidents go unreported or aren’t properly vetted by supervisors.

One longtime human resources official interviewed by investigators said a ‘‘laissez faire’’ attitude exists of ‘‘what happens on the river, stays on the river.’’ Grand Canyon officials until recently allowed river rafters to bring alcohol on the trips.

A National Parks Service spokesman said the agency has zero tolerance for the behavior cited in the report.

‘‘No NPS employee should ever experience the kind of behavior outlined in the report, and it is even more disappointing because previous efforts to change the culture at the River District of the Grand Canyon failed to improve working conditions,’’ Parks Service spokesman James Doyle said in an e-mail. He said the agency is mulling more changes, including requiring nightly check-in calls, having a supervisor on every river trip, and establishing an ombudsman.

Incidents of sexual harassment on the national park trips included a boatman photographing an employee under her skirt, a supervisor grabbing a contract employee’s crotch, and park employees twerking during a dance party as a river trip was wrapping up, according to the report.

Associated Press