The number of reported sexual offences on British railways, including the Tube, has doubled in five years.
Data obtained under the Freedom of Information Act showed there were 2,382 such crimes reported on trains and at stations last year – up from 1,049 in 2013.
The numbers released by British Transport Police revealed the youngest victims were aged just six.
This was the case in two instances – one in 2014 and one in 2015 – and arrests were made for both crimes. A total of 1,307 offences were recorded by police in 2014 and 1,795 in 2015.
In 2017, there were 210 incidents involving children under the age of 18 and 185 of a total of 2,070 in 2016.
British Transport Police has run the Report It To Stop It campaign since April 2015 to encourage victims of any unwanted sexual behaviour to come forward.
A force spokesman said: “Tackling all forms of unwanted sexual behaviour on public transport is a priority for British Transport Police and we have worked hard in recent years to send a clear message to victims that they will be taken seriously and we will thoroughly investigate offences.
“With the campaign in place since April 2015, we fully expected to record a rise in sexual offences and, though it is clearly a concern that so many people are affected by this type of crime, it is pleasing that previously reluctant victims of sexual offences now have the confidence to report this to us.
“We take every report of unwanted sexual behaviour seriously and have specially-trained officers to find those responsible.
“Thankfully, the rail network is CCTV rich and we use this extensive network of cameras to catch offenders and make it a hostile environment from perpetrators to operate.”