The number of sex assaults on London’s Underground and Overground rail networks rose to the highest level in the past five years in 2013, it was revealed today.

There were 403 cases in London in the 12 months to January 2014, compared with 310 the previous year, according to statistics obtained by London Live, the Standard’s sister TV station. The increase coincides with the launch of a police operation to raise awareness of sex attacks on the Tube and trains.

The figures, obtained in a Freedom of Information request, show 367 of the victims were women, with 88 cases leading to a suspect being charged. Liverpool Street station recorded the highest number of alleged assaults, with 25 taking place within the station’s Tube network.

Police say the increase follows the Project Guardian operation to increase people’s confidence in reporting assaults. Statistics suggest there is a huge under-reporting of sex attacks, with surveys showing 15 per cent of women have experienced attacks or “ unwarranted sexual behaviour” on trains although about 95 per cent of those incidents are not reported.

But since Project Guardian was publicly launched in July last year, the number of sex assaults reported by passengers has risen by 26 per cent.

Inspector Ricky Twyford, the project’s manager, said: “We know there is huge under-reporting and the aim of this operation is to give anybody who may experience a sexual offence or unwanted sexual behaviour on London’s public transport system the confidence to report it.

“We believe the increase in the number of reported attacks is due to a rise in confidence rather than an increase in the number of incidents.”

Other stations with reported sexual assaults that reached double figures last year were the Bank-Monument complex, King’s Cross St Pancras, Oxford Circus and Stratford.

Sylvia, a 25-year-old student, told London Live that she had experience of unwanted attention on the Tube, with a man following her into an empty carriage and sitting next to her.

She added: “He put his coat on his lap and suddenly I saw his hand moving. That’s the moment I stood up. I think he realised I knew what he was doing and he got off the Tube the next stop.”

The number of sex attacks has fallen compared with 10 years ago, when 1,120 were reported on the Tube and Overground in London.

A TfL spokesman said increases in reported offences — “a crime type we know has historically been under-reported” — are a direct result of Project Guardian.