As far as police know, the shooting of Tanesha Melbourne (pictured), 17, in Tottenham was more or less random

As far as police know, the shooting of Tanesha Melbourne was more or less random. The 17-year-old was chatting with friends in the street close to her home in Tottenham, North London, when a gunman in a moving car fired at least twice at the group.

Tanesha was hit in the chest and collapsed. Her mother, hearing the gunfire that witnesses described as ‘like fireworks’, came rushing out. Her teenage daughter died in her arms. No mother should ever have to suffer such an appalling loss.

That tragedy unfolded at about 9.30pm on Bank Holiday Monday. Incredibly, it is not even the most recent gun attack on the streets of London this month. About an hour after Tanesha’s killing, police were called to Walthamstow in East London, where a youth of 16 died after being shot and another 15-year-old was stabbed.

The staggering statistics are that 48 people have been murdered in the capital so far this year. For the first time in modern history, London is more deadly than New York. Rates of rape and robbery were already higher than in the city once called the crime metropolis of America.

That is not a shallow comparison. London and New York not only have populations of similar sizes, about eight million, but a similar annual police budget: approximately £3 billion.

Yet the U.S. city invests in about 25 per cent more officers — 40,000, compared to our 32,000. The Met also have to carry responsibility for counter-terrorism, which is handled in America by Homeland Security, a different branch of law enforcement.

I believe that a crisis of violence on our streets threatens British society on a scale that has not been seen before.

It represents a monstrous challenge for the police, who cannot defeat it alone. To turn the tide of shootings, stabbings and vicious muggings, we must all act together. Only a co-ordinated response can halt this slide into murderous anarchy.

Let’s be clear straight away: the situation is far from hopeless. There’s strong evidence that we can reverse the trend, and it comes from New York — a city so lawless in the Seventies and Eighties that gangs of criminals seemed free to rob and kill as they pleased, and murder was a daily occurrence.

That changed, thanks to a rigorous policy of ‘zero tolerance’ to all crime.

When I was Home Secretary in 2003, I invited the police chief who masterminded that scheme, Commissioner William J. Bratton, to Britain. His advice wasn’t welcomed on all sides, particularly among senior Met Police officers.

But I was convinced we needed to hear what Commissioner Bratton had learned, not only in the Big Apple but in Boston, another East Coast U.S. city where zero tolerance had helped to drive down crime dramatically.

Here in the UK, the very opposite now seems to be happening. Part of the problem for the Met in trying to implement zero tolerance is that their powers to stop-and-search have been sharply reduced.

Twenty years ago, there was a perception that these powers were being widely misused, and many black people felt that police treated stop-and-search as a licence to do with them as they pleased.

As a result the power was reined in — to the point where police are hampered during routine enquiries. Anecdotal evidence suggests many officers avoid carrying out searches on black youths for fear of being accused of racism, and because the box-ticking paperwork is too time-consuming.

The pendulum has swung back too far, making it easy for youths to carry knives and guns without much risk of being caught. This has to end. No one should have the freedom to carry a concealed weapon just because police are afraid to look for it.

The figures speak for themselves. Since 2014 — when Theresa May (who was then Home Secretary) ruled that stop-and-search can be used only when police feel a crime ‘will’ take place, rather than ‘might’ — knife crime has risen dramatically.

While searches on the streets have been reduced by about two-thirds, knife offences have soared to their worst levels in a decade.

The police need more manpower. It’s not just bobbies on the beat: we need DNA analysts, forensic scientists and scene-of-crime officers.

But to my mind, the biggest difference between violent crime today and when I was in government is the dangerous influence of social media. Viral videos make the unthinkable seem normal in no time at all.

When I was Home Secretary in 2003, I invited the police chief who masterminded that scheme, Commissioner William J. Bratton, to Britain (pictured together in 2002)

I believe this is the only explanation for the horrific increase in acid attacks over the past two years for example. In a flash, they went from being a nightmarish exception, first seen in domestic abuse cases in India and other countries, to a recurring terror in Britain.

Videos of the sickening attacks — in which female victims were targeted in particular — were shared online. And suddenly, acid attacks seemed as common as other muggings. Gangs of callous louts rode around London and other UK cities with plastic pots of liquid acid, which they hurled into people’s eyes — sometimes during a robbery; often for no reason at all.

Some young gang members claimed that acid was popular because it was easier to conceal than a knife or a gun, and the evidence could be tipped away. But I think the real reason is cruder than that. It’s a fashion, a sick viral cult spread by the internet.

Scotland Yard Commissioner Cressida Dick has underscored the dangers of online sites in escalating crime: ‘There’s definitely something about the impact of social media,’ she said this week, ‘in terms of people being able to go from slightly angry with each other to “fight” very quickly.’

The speed of communication and its inflammatory nature is the very devil, and controlling social media seems beyond any human power. But giving up, accepting the inevitable deaths of more innocents, is not an option.

There is another area, too, that’s vital in our efforts to bring an end to this violence — something that Commissioner Bratton with his zero tolerance approach highlighted: working with the community.

In the late Nineties, when I was in government, we launched Operation Trident to help tackle black-on-black gun crime. Its aim was to glue fractured communities back together, with input from black churches and youth organisations as well as community leaders.

They provided us with vital intelligence and helped turn potential criminals away from guns and knives.

We saw fantastic results from sports organisations such as boxing academies, and by reaching out to everyone in those places most affected we found communities were more than willing to help.

Friends and family lay flowers at the scene where Tanesha Melbourne was shot and killed in Tottenham, North London

Over the years, I suspect, the contacts and trust we built under Operation Trident have been eroded. They require nurturing to remain strong.

The key is to recognise that those same communities from which gangs and violent criminals emerge are the ones which suffer most from their campaigns of violence.

That is why the recent announcement by the Mayor of London to put ‘seed funding’ into local initiatives and £45m into much-needed youth provision has to be welcomed. When local and central government back the best of community initiatives in support of the police, it can only help crack this upsurge in violent crime.

Targeting the perpetrators is not enough. We have to empower everyone in the communities concerned to stand up and say: ‘We will not accept these deaths on our streets any longer.’ A combined effort will achieve much more than the police can on their own.

Only by employing all the methods that we know from long experience will reduce violent crime might we see an end to senseless murders like that of Tanesha Melbourne. We need a zero tolerance policy to crime, and an effective stop-and-search policy.

Crucially, we need action by social media platforms, which now bear such a heavy burden of responsibility for the carnage taking place on our streets.