The 287-page report from the Office of the Independent Police Review Director may lead to charges against police officers and could bolster numerous civil lawsuits filed against the police.

Although security for the summit meeting, as well as a preceding Group of 8 meeting north of Toronto, was the most costly police effort in Canadian history -- the final tally was about $1 billion -- the result was widely criticized.

Early in the summit meeting, a small group of violent protesters went on a looting rampage through downtown Toronto's main shopping district unmolested by police.

After that, however, police swung into action, ultimately arresting 1,100 people, most of whom were later released without charges. Many of those arrested and held were peaceful protesters or passers-by. Others were arrested in homes and other residences without proper warrants, the report said.

The report casts much of the blame on Tony Warr, the deputy police chief for Toronto, who ordered subordinates to "take back the streets." The incident commander in charge at the time told investigators that Deputy Chief Warr "wanted the streets that had been made unsafe by the terrorists that were attacking our city to be made safe again by restoring order."

The report found that his orders were followed in ways that not only broke the law but often involved excessive force.

"Without question, the attitude of senior officers toward protesters and toward the rules of their own services influences the behavior of police on the ground and sets the tone for the police response," the report said. "It allows individual officers, who find out they can act with impunity, to use excessive force."

It added, "Numerous police officers used excessive force when arresting individuals and seemed to send a message that violence would be met with violence."

Once arrested, the people detained were held in a makeshift prison in a former film studio.

The independent investigation found that the temporary prison was swiftly overwhelmed by the large number of people arrested. Only a single computer was provided to process records for court hearings. Prisoners' cases were incorrectly or minimally documented, while youths were locked up with adults, the investigation found.

Most prisoners, the report found, were denied access to lawyers, a violation of their constitutional rights, not given access to phones, another legal violation, and many were held for hours in cells without toilets or not given food and water.

"Considering the conditions within the prisoner processing center -- the overcrowding, lack of food and water, lack of access to toilets, and the additional duties placed on the staff -- it is remarkable that no serious incident occurred," the report said.

The report makes 42 recommendations, including a law requiring the police to disclose evidence of potential wrongdoing by officers.

Bill Blair, Toronto's chief of police, declined to apologize for his force at a news conference. He said, however, that about two dozen complaints against specific officers forwarded by the independent investigation would "likely" lead to disciplinary hearings.

A Toronto police constable already faces a criminal charge of assault causing bodily harm related to the arrest of one protester.