SAN DIEGO - A widely touted Border Patrol initiative to send migrants back to Mexico far from the points they are caught entering the United States illegally has one of the worst track records at discouraging people from trying again, according to a new study that offers a detailed assessment of how the agency's new enforcement strategies are working.

The aim of the so-called lateral repatriations is to make it more difficult for migrants to reconnect with smugglers. The Congressional Research Service, drawing on previously unpublished Border Patrol data, found those migrants were among the most likely to get caught again.

The study, which was delivered to members of Congress earlier this month but not publicly released, also found that criminal prosecutions and placement in formal deportation proceedings appeared to be the most effective deterrents.

Nearly 102,000 arrests on the Mexican border were channeled to the Alien Transfer Exit Program during the 2012 fiscal year, which typically involves putting migrants caught in Arizona on buses to be sent back to Mexico hundreds of miles away at crossing points in Del Rio, Texas; Calexico, Calif.; and San Diego. The report says 24 percent of migrants who received such treatment during the 2012 fiscal year were caught again, compared with a recidivism rate of 17 percent overall along the border.

The gap was slightly wider in 2011, when 28 percent of crossers who were assigned lateral repatriation were caught again. That compared with an overall rate of 20 percent along the border.

The report does not explain why some return methods appeared to work better than others but noted that the Border Patrol looks at the history of each migrant before deciding which method would be the most successful.

Bryan Roberts, who held positions as an analyst of border and immigration issues at Homeland Security, said smugglers may form alliances in distant cities to connect migrants with other guides. For example, a smuggler in Naco, Ariz., may call one in Brownsville, Texas, if his customer is bused there, to arrange another try.

Lateral repatriations performed better than simply turning migrants back to Mexico without any punishment.