A two-year investigation by the Justice Department found patterns of “outrageous” conduct by the police in Worcester, Mass., including excessive use of force and sexual contact between undercover officers and women suspected of prostitution.

In a report released on Monday, the department’s civil rights division detailed police misconduct dating back at least five years in Worcester, a city of 207,000 in central Massachusetts. It corroborated repeated reports by women’s advocates in the city that officers had “tricked or misled” women suspected of being prostitutes into providing sex acts and “offered less, or no, punishment in exchange for sex.”

Federal investigators found that the Worcester Police Department’s “inadequate” policies, training, supervision, investigations and discipline “fostered these unlawful patterns.” They also raised “serious concerns” that the department’s enforcement practices could result in biased and discriminatory policing of Black and Hispanic residents, who were disproportionately arrested and subjected to force, according to the report.

Brian T. Kelly, a lawyer representing the Police Department, criticized what he called “an unfair, inaccurate and biased report which unfairly smears the entire Worcester police force” instead of targeting individual officers “who could, and should, be prosecuted if these serious allegations are true.”

Mr. Kelly said that the report was “riddled with factual inaccuracies" and that it ignored information provided by the city that “debunks many of the anonymous claims.”