The country's leading police officer on gang culture warns today that gang members are getting younger and that they are resorting to lethal violence much more swiftly for the most trivial slights.

In an interview with the Guardian, Commander Sue Akers of the Metropolitan police identified other trends, including the emergence of a small number of girl gangs, and how women are being used to carry and conceal weapons.

Speaking at the end of a week in which Sean Mercer, 18, was convicted of murdering 11-year-old Rhys Jones, Akers said the only way to counter the threat of further violence was long-term investment that offers gang members a real alternative to crime. Mercer was 16 at the time of the killing.

"You can carry on with a stick, but you need a carrot at the end of the day," said Akers. "Some of the gang members go to prison and, when they come out, they get back into the gangs, because life doesn't seem to offer them much else."

The rise in teenage gang crime is turning into a priority issue for ministers. There have been 66 teenage murders in Britain this year, mainly knife attacks. London has had 30 murders; there were six in Scotland, five in Greater Manchester and four in Merseyside. The British Crime Survey is to start documenting the number of teenage murders separately. The government has also launched a new programme to tackle gang crime.

Akers, the spokesperson on gangs for the Association of Chief Police Officers and one of the Met's most experienced officers in the field, told the Guardian: "We're seeing young kids killing other young kids. We've seen 14- and 15-year-olds being killed over what seems the most trivial slights or just a glance. In the past, they would use violence over something like enforcing debts but now it's over this 'respect' issue, the smallest insult."

Gangs no longer split down racial lines but were formed as a result of territory, neighbourhood or shared interest. "There is less focus on ethnicity now," she said.

Akers said people must distinguish between youths who hang around together on street corners and may commit minor antisocial offences and the real gangs involved in violence and criminality. A growing number of senior officers advocate offering alternatives to gang life. She pointed to work being done in Glasgow, similar to the Boston Ceasefire project in the US. Police tactics can have an immediate effect, she said, citing the apparent success of stop-and-search in London. "But - and it is a big but - if there are no alternatives for gang members, then they just go back to it. It takes time and investment. We need to get really, really focused on the very young."

British gangs differ from US gangs in structure and hierarchy, she said. "Ours are more fluid and more fickle. Gangs disappear and fragment, they can be allies one week and not another." A small number of girl gangs had emerged in London, "and some gangs use women to look after their weapons". The vast majority remained young men and boys.