"We intend to aggressively prosecute this case," Attorney General Loretta Lynch told reporters Wednesday, "and we intend to prevail."
Authorities had no choice but to file a lawsuit after the Ferguson City Council voted Tuesday to change the terms of a deal negotiators had been hashing out for months, Lynch said.
"The residents of Ferguson have suffered the deprivation of their constitutional rights, the rights guaranteed to all Americans, for decades. They have waited decades for justice," Lynch said. "They should not be forced to wait any longer."
The lawsuit alleges a pattern and practice of unconstitutional police conduct in the city.
A city spokesman told CNN that officials will have no comment about the Justice Department's lawsuit until Thursday.
Ferguson officials have not seen the lawsuit, city spokesman Jeff Small said.
Negotiations over reforms to the city's police force and municipal court system began after a Justice Department investigation last year found the Ferguson Police Department had discriminated against African-Americans
, targeting them disproportionately for traffic stops, use of force and jail sentences.
"These violations were not only egregious, they were routine. They were encouraged by the city in the interest of raising revenue," Lynch said Wednesday. "They were driven, at least in part, by racial bias and they occurred disproportionately against African American residents of Ferguson."
City officials have said their Tuesday vote wasn't a rejection of a deal with the Justice Department but was rather a push to return to the table and change some of the terms out of concerns over costs.
Lynch said the council knowingly voted against an agreement approved by the city's own negotiators.
"The city was well aware that by deciding not to accept it, they were choosing litigation," she said. "This was their choice."
City Council proposed seven amendments
In a unanimous vote Tuesday night, council members approved the deal -- but only if the Justice Department accepts seven amendments.
The Justice Department wasn't expecting any changes to the negotiated deal and wasted little time in responding.
"The Ferguson City Council has attempted to unilaterally amend the negotiated agreement," Vanita Gupta, head of the agency's Civil Rights Division, said in a statement
. "Their vote to do so creates an unnecessary delay in the essential work to bring constitutional policing to the city, and marks an unfortunate outcome for concerned community members and Ferguson police officers."
The national spotlight on Ferguson began after the fatal shooting of 18-year-old Michael Brown
by Officer Darren Wilson in August 2014. Brown, who was unarmed, was black, and Wilson is white. Brown's death prompted days of protests and riots in Ferguson and a national conversation about the role of race in police interactions with citizens.
Reaction to the City Council vote was mixed, the St. Louis Post-Dispatch reported
One activist, Debra Kennedy, called the public hearings "a farce, because the DOJ is not going to go back and renegotiate," the newspaper reported. "It was like a 'no' vote."
Others chanted, "You can't amend justice," according to the Post-Dispatch.
Seven months of negotiation
The agreement that City Council wants to change was negotiated over seven months between the city and the Justice Department.
"Although we did not get everything we wanted in the agreement, we certainly made sure that what was agreed upon can be implemented in a timely and sufficient manner," Ferguson Mayor James Knowles III said of the consent decree the city received January 26.
"We're not trying to take away any safeguards," Knowles told CNN affiliate KMOV
. "We're not trying to take away anything substantive out of the decree."
City Councilwoman Ella James agreed.
"There are some things in the consent decree that we're asking to be amended, but all in all I think we're moving forward, we're moving in a positive direction," she told CNN affiliate KTVI.
What City Council wants
The original agreement
would require the city to hire additional senior staff dedicated to the implementation of the deal and in areas such as crisis intervention and community-police relations. Other costs to the city of Ferguson would include the creation of an electronic complaint tracking system, an early intervention system and training throughout various levels of the police department.
In its amendments, the City Council demanded the following changes in order for the decree to go into effect:
• That it contains no mandate for the payment of additional salary to police or other city employees.
• That it contains no mandate for staffing at the city's jail.
• That the deadlines set forth are extended.
• That the terms do not apply to other agencies that take over services currently provided by the city.
• That a provision for local preference in contractors and consultants is included.
• That goals for minority and women participation in consulting, oversight and third-party services are included.
• That monitoring fee caps are changed to $1 million over the first five years and no more than $250,000 in any single year.
'Just sign it'
Spirited public input preceded Tuesday night's vote.
"Black lives matter! Black lives matter!" chanted one community member.
Another suggested it was time to wrap up this chapter in the city's history.
"It's time to stop. Just go and sign the decree. You still haven`t settled the Mike Brown settlement," he said. "Get it done. Just sign it."
Brown's parents filed a wrongful death suit
against the city in April.
Justice Department found pattern of discrimination
The 102-page report
issued by the Justice Department last March said some Ferguson police officers saw residents as "sources of revenue," leading to practices that federal investigators said disproportionately targeted black residents.
It also found evidence of racist jokes sent by some Ferguson police officers and court officials.
The department made 26 recommendations, including:
• Ferguson police provide training to ensure officers aren't using bias in policing.
• Officers practice community policing by getting out of cars and getting to know communities.
• Focus police stops, searches and ticketing on protecting the public, as opposed to fund-raising for the city.
Also in March, the Justice Department declined to bring civil rights charges against Wilson
in Brown's death. Justice Department investigators concluded Brown was moving toward the officer when Wilson fired.