Eighty per cent of the white residents in Mississippi’s majority-Black capital city would be included in a proposed new judicial district with hand-selected prosecutors and judges, an analysis by the Guardian has found, leading to further allegations of deliberate racial prejudice in a Republican-backed bill.

The measure would increase the geographic size of an improvement district in the downtown area of the city of Jackson from 7.8 square miles to 25 square miles. It would create a new unelected judicial district within the city, with two judges, two prosecutors and two public defenders.

The judges would be appointed by Mississippi’s chief supreme court justice, Michael K Randolf, a conservative who is white. The prosecutors would be appointed by the state attorney general, Lynn Fitch, a white Republican. The district would be policed with an expansion of the Mississippi capitol police whose chief, Bo Luckey, is white, in a role appointed by the Mississippi commissioner of public safety, Sean Tindell, who is also white.

“No serious person can look at this map and this data and claim the proposed CCID boundaries weren’t drawn to make sure as many white Jacksonians as possible get the ‘benefit’ of a special police force and court filled with hand-picked judges and prosecutors,” said Cliff Johnson, director of the Roderick and Solange MacArthur Justice Center.

Eighty-two per cent of Jackson’s residents are Black, but the new district would incorporate all of the city’s significantly populated white-majority neighborhoods. It would only leave about 5,000 white residents of Jackson living within the city’s remaining law enforcement boundaries. About a quarter of Jackson’s Black residents would be included in the district.

“This bill, and many others that have accompanied it in this legislative session, are all an attack on Black leadership,” said Jackson’s mayor, Chokwe Lumumba. “This is a racist act.”

The Guardian mapped the proposed district using boundaries supplied by the Mississippi legislature’s reapportionment office and data from the US census. The analysis also reveals that the new district would encompass 36% of the city’s entire population, limiting city and county law enforcement power over a third of Jackson.

The bill’s Republican proponents in the Mississippi legislature have argued it is designed to assist the city in dealing with rising crime and criminal court backlogs. But Lumumba insisted the area within the district had some of the city’s lowest crime rates, and pointed out that the courts would also hear civil and chancery matters as well as criminal cases.

“Your data proves what this is really about,” Lumumba said. “These numbers prove there is no merit to their [Republican] claim. And so it is apartheid in Jackson, Mississippi.”

Trey Lamar, the Republican representative who introduced the legislation, did not respond to interview requests.

The bill, which passed the Mississippi house of representatives in a 76-38 vote last week, largely on party lines, will travel to the Republican-dominated senate. If it is signed into law, civil rights advocates expect a number of legal challenges to follow in state and federal court due to alleged violations of the Voting Rights Act and the Mississippi state constitution.

“Should the senate pass house bill 1020 and force us to sue in federal court, which I assure you we would do, this map is Exhibit 1 of discriminatory intent,” Johnson said.

Mississippi’s Republican governor, Tate Reeves, and the attorney general’s office did not respond to requests for comment. A spokesman for the state supreme court justice declined to comment.

Mayor Chokwe Lumumba called the bill ‘a racist act’. Photograph: Michael M Santiago/Getty Images

The proposal echoes laws that Mississippi enacted in the 1960s that did away with some local elected positions and replaced them with appointed officials, said Peyton McCrary, a former historian in the US justice department’s civil rights division.

“Back in 1966, right after the adoption of the Voting Rights Act, several different offices were switched from election to appointment,” he said. “And in other instances, the election was switched from single-member districts to at-large elections. All reflecting the concern of the Mississippi legislature that Black people now were going to be voting in significant numbers.”

Until 2013, when the US supreme court struck down a key provision of the Voting Rights Act, Mississippi had to get election changes approved by the federal government before they went into effect. Had the state submitted the proposal for the new district, McCrary said, he was certain it would not have been approved.

“It would have been rejected soundly. I have no doubt that it would have been rejected. It would pretty much have been an open-and-shut case,” he said.

Amir Badat, a voting rights lawyer with the NAACP Legal Defense and Educational Fund, said: “It very clearly eliminates the voting power on the part of Black voters in Jackson and in Hinds county.” He added: “There is a strong case to be made that the legislature has clearly been put on notice of the disparate impact that this would have on Black people.”

The proposed district covers more than 20% of the city geographically. Badat said the comparisons to apartheid “really resonate”.

“It essentially tells Black residents of Jackson who might come to this district for shopping or eating – it has a lot of some of the big businesses in Jackson that people all across the city come to to patronize or to work at – I think it tells Jackson’s majority-Black population: ‘You’re not welcome here.’”

Badat added that the bill was part of a nationwide trend in which increasingly Republican state legislatures are moving to exert more control over jurisdictions where there are large Black populations. For example, he said, there was a proposal in Missouri that would appoint a special prosecutor to handle crime in St Louis.

In Jackson, residents and advocacy groups have expressed concern about the proposed expansion of the capitol police force, a department created in 2021 and initially tasked with patrolling state government buildings in the city.

The force, which has expanded significantly in the past year, has been involved in a number of controversial use-of-force incidents in recent months. In September 2022, 25-year-old Jaylen Lewis was shot dead during an incident following a traffic stop. The department, which patrols an area less than eight square miles, has been involved in at least four officer-involved shootings since its creation, according to the Mississippi Free Press.

A separate bill in the Mississippi senate seeks to expand the department’s authority over the entire city.

The force did not respond to a request for comment.