Rapes recorded by the Met have risen by almost 20 per cent in a year and policing chiefs have warned that the new figures could reflect a genuine increase in sex attacks in the capital.

Police recorded 7,613 rapes in the 12 months to the end of January compared with 6,392 for the previous year.

Rises in recorded rapes have in the past been attributed to increased confidence among victims to report crimes, rather than a growth in the number of attacks.

But London’s Deputy Mayor for Policing and Crime, Sophie Linden, has warned that the latest figures could point to an “increase in actual sexual violence and rape offending”. Met Deputy Commissioner Sir Craig Mackey also said that “there is something going on with sexual offending in London” and that a rise in the number of attacks was one possible explanation.

Asked at a London Assembly hearing if he had any idea what was behind the rise, Sir Craig said: “No, is the honest answer. It’s not as simple as saying this is increased confidence. Of course, that plays a part but there is something going on with sexual offending in London that we don’t fully understand, the causes of it. We see the end of it, [but] we don’t understand the causes.”

Ms Linden agreed that the rise could not only be explained by a greater willingness to report crimes.

The figures, from the Mayor’s Office for Policing and Crime, also show an eight per cent increase in other sexual offences in the past year, bringing the total number of reported rapes and sexual assaults in London to almost 20,000. Campaigners have suggested the real figure could be “significantly higher” once unreported attacks are taken into account.

London Assembly member Susan Hall, who highlighted the rape figures, demanded action to try to explain the rises. “In recent years, any rise in the number of rapes has largely been attributed to increased reporting — a positive and welcome cultural shift,” she said.

“That, though, cannot explain a jump of almost 20 per cent in just a year, and the Met must urgently look at why we have seen such a radical rise in incidents.”

Mary Mason, chief executive of Solace Women’s Aid, which offers support to the victims of domestic and sexual violence, said campaigns such as the #MeToo movement had helped drive a “cultural shift” in the way sex crimes are treated.

But she added: “The vast majority of survivors we work with still do not report the horrific violence and abuse they experience to the police because they are frightened or ashamed, or concerned about the impact on those around them.

“The statistics matter but they don’t begin to tell you of the trauma, devastation and the psychological pain that rape and sexual assault victims experience. Without help some women end up self-harming and feel like ending it all. Some women do die.”

A spokeswoman for the Met said the force anticipates the number of reported rapes will rise for the next two to five years as reporting of attacks becomes more widespread.

She added: “The Met recognises that around 85 per cent of rape allegations involve parties already known to one another, with individuals experiencing domestic abuse often at higher risk of rape or sexual offences.

“Therefore we also take part in awareness-raising campaigns such as It’s Not OK to combat myths about sexual offences which may discourage people from coming forward and reporting their experiences.”