The Big Question: Do the facts and figures behind knife crime justify the public's fears?

Why are we asking this now?

Alarm is growing that Britain faces an unprecedented wave of knife crime among teenagers following the murder of 15 London youngsters so far this year. The worry for police and parents is that a vicious cycle is beginning: the more headlines there are about knife crime, the more youngsters start to carry blades for their own safety.

The Government has launched a stream of initiatives to tackle the threat and the Home Office yesterday disclosed it was adopting shock tactics in a new advertising campaign against youth violence. The graphic images – devised by young people themselves – include pictures of gaping wounds and of a man with a knife and screwdriver in his chest. They will appear over the next three years in newspaper, radio, website and mobile phone advertisements as well as "viral ads" to be distributed through social networking sites such as Bebo. The Metropolitan Police also disclosed that it had seized 193 weapons – including carving knives – in a two-week blitz on knife crime ordered by the new London Mayor, Boris Johnson.

So is the problem getting worse?

Not according to the British Crime Survey (BCS), which has found that knife crime has consistently accounted for between five and eight per cent of violent offences over the last decade. An estimated 168,000 (seven per cent) of the 2.4 million violent offences in 2006-07 involved knives. That compared with five per cent, or 180,000, of the 3.6 million violent incidents in 1996. Knives were used in 62,720 of the 392,000 muggings last year and 44,700 of the 894,000 incidents of "stranger violence".

The latest police statistics – predating this year's spate of killings in London – also find that the number of murders using a knife or sharp instrument is broadly stable. There were 258 in 2006/07, compared with 261 five years earlier. But Richard Garside, the director of the Centre for Crime and Justice Studies (CCJS) at King's College in London, has noted: "The average age of homicide victims overall has been going down, with younger and younger victims."

Alf Hitchcock, deputy assistant commissioner of the Metropolitan Police, has observed the same trend: "The age of offenders and victims has decreased from mid-teens to early twenties, to early to mid-teens." He also said the severity of injuries inflicted by knives is increasing. His conclusion is reinforced by the 5,240 emergency hospital admissions last year as a result of "assault by a sharp object" – a figure that has risen steadily over the last decade.

How reliable are the statistics?

The statistics on the extent of knife crime are extremely patchy – for instance the police have only started keeping figures for attempted murder, wounding and robbery involving knives since last April. The BCS, based on interviews with members of the public and regarded as the most reliable measure of offending levels, does not currently include the experiences of the under-16s. Critics also say the BCS finds it harder to carry out research in the inner-city areas most likely to be blighted by violent crime.

However, it is possible to discern broad trends and to conclude that there is no national epidemic of stabbings and woundings. But there are hotspots – including London, Glasgow, Manchester and Birmingham – where levels of knife crime are causing alarm.

What about knife carrying in general?

A Home Office survey three years ago found that four per cent of 10 to 25-year-olds had carried a knife in the previous 12 months, rising to seven per cent of 16 and 17-year-olds.

Most carried penknives or flick knives and the vast majority said they carried them only "once or twice" over the last year. The vast majority (85 per cent) said they had a knife for their own protection, with seven per cent using it to threaten others and two per cent to harm someone.

Do knife amnesties work at all?

A five-week national amnesty resulted in an apparently impressive haul of nearly 90,000 weapons in May and June 2006, but it is worth bearing in mind that it represented a tiny fraction of the number of knives in Britain. If each household only has one kitchen knife each then there are 22 million in the country. The CCJS has warned: "It is likely that those people who routinely carry a knife for protection or intend to use a knife in crime will not be safely disposing of their knives in the bins provided at police stations." Numbers of serious stabbings in Strathclyde fell for almost a year after an amnesty in 1993, but then returned to even higher levels.

What actionis being taken by the Government?

The 2007 Violent Crime Reduction Act doubled the maximum sentence to four years for possessing a knife or blade in a public place without good reason and made it an offence, also carrying a jail sentence of up to four years, to use someone to look after a weapon. It raised the age at which someone can legally be sold a knife from 16 to 18 and gave teachers the power to search pupils for weapons.

Jacqui Smith, the Home Secretary, has also raised the prospect of airport-style metal detectors being fitted in some schools in an effort to deter pupils from carrying knives. She said: "I want young people to know it doesn't make them safer to carry a knife – it actually makes them more likely to be a victim."

Police are being encouraged to carry out more stop-and-searches of young people suspected of carrying blades, although there are fears that the tactic could stoke up resentment among ethnic minorities, who have previously found themselves disproportionately singled out by officers.

What about prevention and education?

The Government has increased investment in youth services in an effort to offer alternatives to youngsters who might otherwise be roaming the streets.

A series of programmes which attempt to raise awareness among teenagers of the dangers of knife crime have been run in schools. One key message is to dispel the myth that it is macho to carry a blade.

The new Home Office advertising blitz is the most dramatic attempt so far to bring home the perils of knives to the group of people most likely to be stabbed.

But Sir Ian Blair, the Metropolitan Police Commissioner, yesterday made clear that work in curbing teenage knife use had to start at home.

He said: "To parents it is tough love time. In addition to conversations about drink, drugs and relationships, there are now conversations about knives."

Is knife crime out of control?

Yes...

* The murder of 15 London teenagers in just five months underlines the extent of the problem

* Hospitals say they are treating growing numbers of patients with serious wounds

* If four per cent of young people sometimes carry knives, then thousands of blades are on the streets

No...

* Violent attacks using a knife remain statistically very rare events in Britain. We shouldn't worry about such an attack

* The numbers of such assaults appear to have remained stable over the last decade

* They are mainly concentrated in a small number of the largest cities – and in particular areas of those cities