At least 1,399 sexual offences were recorded in 2014-15 in England, Scotland and Wales, up 282 on the previous year, according to latest figures released by the British Transport Police (BTP).
BTP said the rise in sex crime figures was mainly due to a campaign to encourage reporting of these offences.
The force launched Project Guardian in 2013 aimed at reducing sexual assault and unwanted sexual behaviour on public transport in London, after a survey suggested that 90 per cent of such attacks went unreported.
"It is worth noting that the chances of being a victim of any crime are small. The use of more officers patrolling late- night trains and at peak periods, as well as our extensive CCTV network, is helping to halt this rise," said BTP Deputy Chief Constable Adrian Hanstock.
Also Read
Officers in uniform and colleagues in plain clothes were deployed to patrol London's transport network to identify offenders and prevent crime.
That led to a campaign called "Report It to Stop It", which was launched in April this year to tackle sexual assault on the London Underground.
It is expected to drive down cases of sexual offences on trains as more and more women are encouraged to report the crime.
BTP said a key priority now was to cut train delays caused by incidents such as vandalism and trespass, after police failed to hit last year's target to reduce rail disruption by 6 per cent.
BTP officers are responsible for policing all railway stations and trains including the London Underground in England, Scotland and Wales.