Attorney General Loretta Lynch, joined by Principal Deputy Assistant Attorney General Vanita Gupta speaks during a news conference at the Justice Department in Washington, Wednesday, Feb. 10, 2016, about Ferguson, Missouri. The federal government sued Ferguson on Wednesday, one day after the city council voted to revise an agreement aimed at improving the way police and courts treat poor people and minorities in the St. Louis suburb. (AP Photo/Carolyn Kaster)Just a day after the Ferguson City Council rejected a negotiated consent decree to oversee policing in the Missouri city, the Justice Department filed a sweeping federal lawsuit alleging local law enforcement had violated the civil rights of minorities over a number of years.

The feds allege that Ferguson police engaged in disproportionate stops, arrests, searches, and uses of force against blacks in the city of 21,000 – and also infringed on minorities’ First and Fourteenth Amendment rights in doing so, according to the suit.

The litigation comes nearly a year after a report found constitutional violations in Ferguson.

“The residents of Ferguson have waited nearly a year for their city to adopt an agreement that would protect their rights and keep them safe,” said Loretta Lynch, the U.S. Attorney General, in a statement. “But 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. They should not be forced to wait any longer.”

The St. Louis suburb first came under the federal microscope in August 2014, when teenager Michael Brown was shot and killed by police. Though the officer was later cleared of criminal charges and left the force, local outrage fueled civil unrest and allegations of systemic racism. A federal report released in March 2015 concluded that law enforcement’s focus on generating revenue, and racial bias, were causing significant social problems in the city.

“Our investigation found that Ferguson’s policing and municipal court practices violate the Constitution, erode trust and undermine public safety,” said Vanita Gupta, principal deputy assistant Attorney General. “Ferguson residents and police officers deserve a law enforcement system that productively and fairly serves the entire community.”

READ MORE: Ferguson Mayor: City Is Willing to Challenge Feds in Court

Ferguson city officials said they had approved the consent decree – but on condition the Justice Department would agree to a series of seven amendments. In a cost analysis posted on the municipal website, the administration claimed that abiding by the consent decree as negotiated would cost the city more than $3 million per year in additional staffing and overhead. Ferguson has an operating budget of $14.5 million annually – and is already in a $2.8-million deficit, local officials said.

“During the past seven months, we have worked very hard to ensure that our negotiations were feasible and realistic for the citizens of Ferguson,” said Mayor James Knowles III. “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.”

However, the feds were nonplussed by the counter-offer – and the claims a plan was not financially feasible.

“As has long been established under law, constitutional protection cannot be denied on the grounds of cost,” wrote Gupta, in a Jan. 27 letter to the city.

The Justice Department has initiated more than 20 civil-rights investigations into law enforcement agencies in the last six years, including, Baltimore and Chicago, which have both featured recent high-profile police-involved deaths. The federal authorities don’t always win in their claims: a federal judge ruled in favor of Alamance County in North Carolina over allegations of biased treatment of Latinos in the community.