In one case reported on May 7, a gang of up to eight people on mopeds broke a tourist’s leg as they tried to steal his watch on upmarket Park Lane.Just one day later, residents in Battersea complained that moped gangs armed with machetes were terrorising them and claimed that police have failed to tackle the threat. “The police don’t chase them so it’s almost a licence to commit crime,” one resident said.Among those targeted is former politician George Osborne, who revealed last week he had been the subject of an unsuccessful mugging. Similar crimes have taken place in Birmingham, Newcastle and Manchester.Figures from the end of last year found crime involving the vehicles had risen by 600 per cent over two years, while yesterday Detective Chief Superintendent Stuart Ryan said there had been 11,389 offences reports in London alone in the last 12 months. Some of these young people have been arrested 60, 70, 80 timesDetective Chief Superintendent Stuart Ryan It is feared criminals may be taking advantage of the Metropolitan Police’s pursuit policy, which was updated in 2015 following the death of an 18-year-old moped rider. “But in general terms, people intent on using vehicles to commit crime on London’s roads must realise their actions will attract a proportionate response from London’s police officers.” It states that drivers can only mount pursuits in rare cases, such as if a rider is involved in a serious offence or if there is a “significant” risk to life, property or national security.Other reports have suggested that criminals are deliberately removing their helmets in a bid to try and get police to stop chasing them because it makes the pursuit more unsafe.In a message made public in error last year, a member of the force’s staff claimed riders were “pretty much impossible to stop” as they remove their helmets and can go through pedestrian barriers.Meanwhile, DCS Ryan admitted teenagers are being arrested dozens of times but do not face any “substantive” punishment.“Some of these young people have been arrested 60, 70, 80 times,” he told the Sun on Sunday. “They keep committing offences, you arrest them and put them in front of the court, the court won’t do anything substantive with them. It is a cycle.” Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. The force is currently tackling the crime in Operation Venice.Detective Chief Superintendent Paul Rickett, the force lead on police pursuits, said they take “full regard of national guidelines”.He said: “The Metropolitan Police Service is clear that pursuit tactics are necessary to apprehend criminals and are an option available to only the most highly trained police drivers.“They are trained to assess the level of risk to the people being pursued, as well as the officers themselves and the wider public… The safety of people directly and indirectly involved in a pursuit incident is paramount and additional safeguards are in place when the vehicle being pursued is a moped or motorcycle. Moped muggings have dramatically increased in the last 12 months, it has emerged amid fears police officers are no longer chasing suspects.More than 11,300 offences have been reported in the capital in the last year, according to one detective, while teenage thieves are being arrested up to 80 times but not sent to jail.Despite the surge, officers are still being told they must wait for a police helicopter to mount a pursuit unless there are exceptional circumstances.The figures come after a spate of muggings in central London, with riders using weapons such as machetes and hammers to intimidate and injure their victims as they try and snatch their mobile phones. Often, the mopeds are stolen.