Almost half of gun crime victims in London's black community refuse to help police investigations, a senior Metropolitan Police officer has said.
Trident has charged more than 20 teenagers with a fatal shooting
Lack of confidence in the police and fear of reprisals stop many answering officers' questions, Det Ch Insp Steve Tyler of Operation Trident said.
He said figures also suggest children are becoming involved in gun crime at an increasingly young age.
Operation Trident investigates gun crime in the black community.
DCI Tyler told a fringe meeting at the Labour Party conference that Operation Trident had never charged a teenager with shooting someone dead until April 2005.
He said: "We have now charged in excess of 20 teenagers with shooting someone dead - the youngest of those was 14.
"In excess of 40% of our victims are unwilling to help with investigations."
He revealed that it was not uncommon for a shooting victim to deny they had been shot and refuse to answer police questions.
"They prefer to deal with it themselves, which is clearly the nightmare scenario," he said.
DCI Tyler also said the Met had funded a new youth worker at the national crime hotline Crimestoppers to boost confidence in the service.
He said: "There is big mistrust of Crimestoppers. They (young black people) believe calls are not anonymous and that calls can be traced.
"Crimestoppers have never breached anyone's anonymity since they came into existence."
Protection for victims
In 2006 there were 79 teenage victims of gun crime in the black community, making up about a third of all shootings in London.
The father of murdered schoolboy Damilola Taylor, Richard, addressed the meeting in Bournemouth organised by children's rights group Kids Count.
Mr Taylor, whose son was stabbed to death in Peckham, south London, in 2000, said: "It has gone up dramatically. It is beyond control at the moment, and it is something we all have to stand up against."
Home Office minister Vernon Coaker said a number of projects were in hand to increase confidence in the protection which can be offered to victims of gun and gang crime.
"There can be no greater priority for the Government than ensuring that in every single community in our country people feel safe," he said.