Top officials of the U.S. Border Patrol failed to act on allegations they received in 2000 and 2001 of widespread kickbacks being paid to border agents in Arizona, and later investigations by the Department of Homeland Security avoided holding high-level officials responsible, said a new government report released yesterday.

The U.S. Office of Special Counsel, an independent agency created to protect government whistle-blowers, said in the report that the current head of the Border Patrol, David V. Aguilar, was informed as early as 2000, when he headed the agency in Arizona, that border agents temporarily assigned there were receiving kickbacks from area landlords, but he did not act. The report was sent to President Bush and Congress.

"It stretches credulity that 45 employees at a single Border Patrol station engaged in a kickback and fraud scheme for a number of years . . . without the knowledge of management," the OSC said in a statement. Homeland Security investigators "appear to have exerted little effort to follow up on evidence identified by [Border Patrol] whistle-blowers that would call into question the statements of its management."

Internal probes by the Justice and Homeland Security departments have found that high-level Border Patrol officials committed no wrongdoing and did not engage in any coverup. In all, of the 68 or so Border Patrol employees suspected of wrongdoing, 45 were punished in some fashion, although almost all were low-ranking agents.

By sidestepping punishment of higher-ups under suspicion, "there is a real risk of creating the appearance of a whitewash," Special Counsel Scott J. Bloch said in a statement.

The controversy harkens to 1999, when waves of undocumented Mexicans were pouring across the U.S. border into Arizona every night. Over the next three years of Operation Safeguard, the Border Patrol dispatched more than 1,000 of its uniformed agents to Arizona for one- to three-month details to try to stanch the flow.

The operation was chaotic from the start, in part because the vast majority of its young, recently hired agents were on their first out-of-town deployment, and supervisors were stretched extremely thin.

Landlords in economically distressed southern Arizona were desperate for the agents' business, and many gave cash rebates to agents, who then exaggerated their rent in official expense claims, internal probes found. In some cases, the landlords paying kickbacks were Border Patrol employees or officials, the probes found.

Two veteran Border Patrol agents in the agency's Tucson sector, Larry E. Davenport and Willie A. Forester, sparked the controversy in 2000 when they complained about the practices to superiors in that sector, the OSC report said.

Two high-ranking Border Patrol officials in the Tucson sector to whom they complained were Rowdy Adams and Carlos Carrillo, both of whom were personally close to Aguilar, then the head of the Border Patrol in that sector. Both followed Aguilar to Washington last summer when he became the Border Patrol's chief.

Adams now is a Border Patrol senior associate chief who oversees technology issues, such as its multibillion-dollar America's Shield Initiative to place cameras and sensors along U.S. borders. Carrillo is also a senior associate chief and a top Aguilar aide.

According to an OSC investigative document obtained by The Washington Post but not released yesterday, whistle-blower Davenport reported his kickback allegations to Adams and Carrillo in fall 2000. "According to Mr. Davenport, Mr. Carrillo advised him that he might not be considered a team player if he reported the matter," that document said.

Davenport said that in February 2001, when he laid out his allegations to Adams and two other Border Patrol officials, he was told to "mind his own business," the report released yesterday said. Adams and Carrillo also told Davenport that "if he wanted to move up in the Border Patrol . . . he had to get along" and drop his complaints.

The two whistle-blowers said that in June 2000 Aguilar contacted a local apartment complex to complain about kickbacks it paid to agents, the report said. Another time, an agent who was a landlord sent Aguilar a memo complaining that another agent demanded kickbacks, but Aguilar "refused to intervene," it said.

Internal probes by the Justice and Homeland Security departments starting in 2003 found Border Patrol managers were uninvolved in the scandal, but the Office of Special Counsel continually prodded them to investigate further and punish higher-ups.

In 2003, DHS officials notified OSC that despite previous promises that it would punish other Border Patrol officials, they had decided not to do so because disciplinary action would be "an administrative burden."

Two more probes by DHS's Customs and Border Protection unit in 2004 "accepted the contentions of the management personnel under investigation despite the existence of contravening evidence," the OSC said.

OSC said yesterday that DHS's investigations of management were deficient and "at best lacked thoroughness."

CBP spokeswoman Kristi M. Clemens said the agency "takes all allegations of misconduct or abuse extremely seriously" and that Commissioner Robert C. Bonner, who heads CBP, "has the highest confidence in Chief Aguilar's leadership and management abilities."

All the kickback allegations of travel improprieties "were investigated and adjudicated," she said. "Those responsible were held accountable."

Border Patrol Chief David V. Aguilar, who headed the Tucson unit, was allegedly informed of the kickback scheme in 2000 but never punished any higher-ups.

OSC's Scott J. Bloch said it "stretches credulity" to say superiors were unaware of the scheme.