The Metropolitan Police's Operation Trident could be broken up as the force looks to save money in the government's Spending Review.
The unit, which investigates gun crime in London's African-Caribbean community, may be merged with other squads to cut costs.
The Trident independent advisory group, which monitors the unit's work, was told the news three weeks ago.
The Met said no decision has been made, but no department was "sacrosanct".
Claudia Webbe, who leads the advisory group, said she had been warned "nothing is off the table".
But she said: "To even think about breaking it up would be sacrilege.
"Any impact on the work of Trident will seriously affect not only the ability to investigate and bring to justice these men of violence who are terrorising the community but it will seriously affect the relationship police have with black communities.
"I think Trident has single-handedly brought up and turned around the image of the Met, particularly when you consider the bad relations that exist over issues like stop-and-search and the progression of ethnic minorities with the service."
The unit was set up in 1998 after killings in Lambeth and Brent.
Senior officers wanted to improve relations with black people who distrusted them and were reluctant to pass on information about even the most serious crimes.
It was eventually implemented across London and expanded further in 2004, taking on responsibility for all non-fatal shootings.
Senior officers may now be considering bringing Trident into the Homicide and Serious Crime Command (HSCC) wing of the Met, which is home to 24 murder investigation teams.
A Met spokesman said "no decisions have been made on any future structuring of Trident", adding that the force was facing "very challenging times" as the full impact of cuts became clear.
"As part of this process, all commands within the Met will be scrutinised to ensure that they deliver their services as effectively and as efficiently as possible," he said.
"It has been made clear to all within the Met that no organisational structures are sacrosanct."