Wasteful spending. Favoritism and nepotism. Sexual harassment.

These were a few of the findings of a four-year Senate investigation into the U.S. Marshals Service, which concluded Thursday. A newly released report has revealed the Justice Department agency was rife with misconduct and abuse of authority, and at high levels.

The Senate Judiciary Committee's report, that included more than 100 interviews with current and former agency employees, details a long list of serious offenses that touched every part of internal affairs.

Those offenses include "wasteful spending on lavish office furnishings, contracts and costly, but rarely-used facilities; inappropriate hiring practices, such as favoritism and nepotism; the use of subordinates to fill out applications for senior executive service positions; and the use of paid and unpaid leave to allow for full retirement benefits of individuals facing substantiated claims of misconduct," according to the memo.

Officials also failed to adequately punish people, including sexual harassment, prostitute solicitations, and in one case in which an employee forged a judge's signature on hundreds of subpoenas.

Judiciary Chairman Chuck Grassley, R-Iowa, said Thursday the initial concerns that triggered the investigation were "only the tip of the iceberg."

"As our investigation progressed, we found a culture of mismanagement, abuse of authority and lax accountability that started clear at the top and has set a terrible standard for other employees across the agency. Poor leadership and pervasive misconduct cripples morale and corrodes trust of employees tasked with apprehending criminals and keeping communities safe. This culture must change," Grassley said in a statement.

In addition, some employees who spoke with Senate investigators lied and whistleblowers were punished for speaking up when rules were broken.

Grassley's committee said new leadership that came in during the investigation has begun to turn around that culture, but he also made recommendations for additional reforms.

Those changes include implementing better training for how to report concerns, improving how employees are paid when going through misconduct investigations, and improving oversight cooperation with Congress.