There have been calls for another national gun amnesty

Speaking at the Association of Chief Police Officers' annual conference in Birmingham, Dep Ch Con Alan Green said the problem must not be ignored.

"I feel the service is going to be in the dock for having shot some young person," he warned on Thursday.

Metropolitan Police chief Cressida Dick added young boys saw guns as "cool".

Some forces need to have a damn good look at themselves Det Ch Con Alan Green, GMP

Mr Green added: "The average age of people carrying ball-bearing guns in Greater Manchester is just 13 years.

"The threat from imitation firearms isn't that of slight injuries to young people, it is that you are likely to shoot someone at the age of 13 in the not too distant future.

"The service will then have to answer some serious questions about what we've done to tackle gun crime."

Home Office permanent secretary Leigh Lewis suggested it may be time for a new national firearms amnesty.

National amnesty

The last amnesty two years ago saw 44,000 guns handed over.

"I think it is striking that a lot of our work in the Home Office is making the link between guns and gangs," he said.

"I wonder if we need a more explicit strategy targeting gang leaders just as we have a strategy targeted on prolific offenders?"

Greater Manchester Police's Mr Green said forces were still "missing massive opportunities" to gather intelligence on gun crime.

"Some forces need to have a damn good look at themselves because they are not making good use of the legislation and tackling the imitation firearm problem," he said.