DENVER — A new report catalogs a range of problems with the way the federal government is managing thousands of wild horses and burros that roam the American West, supporting the position of animal rights advocates who have long argued that the program is ineffective and needlessly cruel.

The report, conducted by the National Academy of Sciences at the behest of the Bureau of Land Management and released Wednesday, concluded that the bureau’s methods of counting the thousands of wild horses and burros that wander rural stretches of the United States were inconsistent and most likely inaccurate.

It also said that the bureau’s policy of removing the animals from the range and taking them to holding facilities as a means of population control, an approach that has drawn sharp criticism from wild horse proponents, did not work. “Continuing ‘business as usual’ will be expensive and unproductive for B.L.M. and the public it serves,” the report said. “Compelling evidence exists that there are more horses and burros on public rangelands than reported at the national level and that population growth rates are high.”

An icon of frontier mythology, wild horses, which trace their lineage to United States Cavalry horses, workhorses and horses brought by Spanish settlers, have been at the center of an increasingly bitter dispute over the past several years. The bureau contends that their numbers have become unmanageable. And it says it has little choice but to bring them to enclosed pastures so that other animals can share the land. Horse advocates counter that the horses should be allowed to live freely.